What does “experiment” mean?

“experiment” means A scientific test done carefully to discover something or to check if an idea is true.. Pronounced /ɪkˈspɛrəmənt/. Close synonyms: test,trial. For example: The experiment was carried out under strict laboratory conditions.

What does “evidence” mean?

“evidence” means Facts or signs that show something is true.. Pronounced /ˈɛvədəns/. Close synonyms: proof. For example: There is strong evidence that the new vaccine works well.

What does “theory” mean?

“theory” means A set of ideas that explains why or how something happens.. Pronounced /ˈθiəri/. Close synonyms: explanation, model, framework. For example: Einstein's theory changed the way we understand time and space.

What does “hypothesis” mean?

“hypothesis” means An idea that scientists test with experiments to see if it is true.. Pronounced /haɪˈpɑθəsɪs/. It is formal. Close synonyms: assumption, proposed explanation. For example: The results of the study did not support our hypothesis.

What does “sample” mean?

“sample” means A small amount of something that shows what the whole thing is like.. Pronounced /ˈsæmpəl/. Close synonyms: specimen, selection, subset. For example: Each sample was analyzed twice to avoid mistakes.

What does “laboratory” mean?

“laboratory” means A room where scientists do experiments and tests.. Pronounced /ˈlæbrəˌtɔri/. Close synonyms: lab. For example: The new laboratory is equipped with the latest technology.

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English B2 — Science & Technology Official

Science, research and technology English at B2, defined in English. Words covering method and evidence, data and devices, energy and environment, each with an English definition, IPA, synonyms and a usage note on the precise sense a scientific text expects.

CEFR B2 — Upper Intermediate

At this level you can follow news, debate topics, write essays. Vocabulary: ~4,000 words (cumulative).

Words in this deck

What does “experiment” mean?: “experiment” means A scientific test done carefully to discover something or to check if an idea is true.. Pronounced /ɪkˈspɛrəmənt/. Close synonyms: test,trial. For example: The experiment was carried out under strict laboratory conditions.
What does “evidence” mean?: “evidence” means Facts or signs that show something is true.. Pronounced /ˈɛvədəns/. Close synonyms: proof. For example: There is strong evidence that the new vaccine works well.
What does “theory” mean?: “theory” means A set of ideas that explains why or how something happens.. Pronounced /ˈθiəri/. Close synonyms: explanation, model, framework. For example: Einstein's theory changed the way we understand time and space.
What does “hypothesis” mean?: “hypothesis” means An idea that scientists test with experiments to see if it is true.. Pronounced /haɪˈpɑθəsɪs/. It is formal. Close synonyms: assumption, proposed explanation. For example: The results of the study did not support our hypothesis.
What does “sample” mean?: “sample” means A small amount of something that shows what the whole thing is like.. Pronounced /ˈsæmpəl/. Close synonyms: specimen, selection, subset. For example: Each sample was analyzed twice to avoid mistakes.
What does “laboratory” mean?: “laboratory” means A room where scientists do experiments and tests.. Pronounced /ˈlæbrəˌtɔri/. Close synonyms: lab. For example: The new laboratory is equipped with the latest technology.

English · definitions in English 250 words ~25 days at 10 words/day 0 downloads B2

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Word List — click grammar notes to expand

Word	Translation	Example
experimentneutral /ɪkˈspɛrəmənt/ A scientific test done carefully to discover something or to check if an idea is true. Synonyms: test,trial	controlled scientific test	The experiment was carried out under strict laboratory conditions.
You carry out, conduct, run or perform an experiment, never make one. The preposition is on for what is tested and with for what is tried: experiments on mice, experiments with light. As a verb it always needs with: experiment with a new method.
evidenceneutral /ˈɛvədəns/ Facts or signs that show something is true. Synonyms: proof	proof; supporting facts	There is strong evidence that the new vaccine works well.
Uncountable, so never an evidence or evidences; say a piece of evidence or some evidence. It takes for or of: evidence for a theory, evidence of damage. Also evidence that plus a clause. Common with strong, clear, little and no.
theoryneutral /ˈθiəri/ A set of ideas that explains why or how something happens. Synonyms: explanation, model, framework	tested explanation; model	Einstein's theory changed the way we understand time and space.
In science a theory is a well tested explanation, not a guess, so the theory of evolution is not a doubt about it. Everyday in theory means on paper but perhaps not in practice. Theory of plus a noun. Related forms: theoretical, theorist.
hypothesisformal /haɪˈpɑθəsɪs/ An idea that scientists test with experiments to see if it is true. Synonyms: assumption, proposed explanation	an idea put up for testing	The results of the study did not support our hypothesis.
The plural is hypotheses, /haɪˈpɑθəsiz/. You form, test, support or reject a hypothesis, and results support rather than prove one. An assumption is taken for granted; a hypothesis exists in order to be tested.
sampleneutral /ˈsæmpəl/ A small amount of something that shows what the whole thing is like. Synonyms: specimen, selection, subset	small representative part	Each sample was analyzed twice to avoid mistakes.
In research it means the people or items actually studied, so a large sample describes the study's size and a random sample how it was chosen. You take, collect or analyze one. A small sample is the standard criticism of a weak study.
laboratoryneutral /ˈlæbrəˌtɔri/ A room where scientists do experiments and tests. Synonyms: lab	science workroom	The new laboratory is equipped with the latest technology.
Stress sits on the first syllable in American English. The short form lab is far more common in speech and in fixed phrases such as lab coat, lab results and lab technician. Before a noun the full form stays: laboratory conditions, laboratory tests.
researcherneutral /ˈrisɜrtʃər/ A person who studies a subject carefully to discover new facts about it. Synonyms: scientist,investigator	person who does research	Researchers have found a link between diet and memory.
Research takes into or on, never about: research into memory, research on bees. A researcher works at, for or with an institution. The noun research is also uncountable, so some research or a piece of research, never researches.
scientistneutral /ˈsaɪəntɪst/ A person who studies science and works with experiments and facts. Synonyms: researcher, expert, academic	science expert	Scientists warn that sea levels are rising faster than expected.
Use it only for a person; the adjective is scientific, so scientific research, not scientist research. Naming the field is normal: a climate scientist, a computer scientist. A scholar may work in any subject, including history or literature.
methodneutral /ˈmɛθəd/ A planned way of doing something, especially in science. Synonyms: technique,way	planned way of working	We used a simple method to measure the speed of the reaction.
A method is the general way of working; a technique is the specific skill used to carry it out. You use, apply, develop or follow a method. Method of plus a noun, method for plus a purpose. The adjective methodical means careful and orderly.
discoveryneutral /dɪˈskʌvəri/ The act of finding something important that nobody knew about before. Synonyms: finding	an important new find	The discovery of penicillin saved millions of lives.
You make a discovery, never do one, and the usual frame is the discovery of a new species. You discover what already existed but invent what did not, so the light bulb was invented rather than discovered.
findingformal /ˈfaɪndɪŋ/ A piece of information that is discovered as the result of research. Synonyms: result,discovery	a research result	The findings were published in an international science journal.
Nearly always plural in research writing: the findings suggest, our findings show. You report, present or publish findings. A finding is what the data showed; a conclusion is what you decided it means.
observationneutral /ˌɑbzərˈveɪʃən/ The act of watching something carefully to learn from it. Synonyms: watching, monitoring, examination	careful watching	Careful observation is essential in any scientific experiment.
Uncountable when it means the activity: under observation, close observation. Countable when it means one recorded measurement or a remark: we made forty observations. The verb is observe and the person an observer.
analysisneutral /əˈnæləsɪs/ The careful study of something to understand it or explain it. Synonyms: examination, study, breakdown	detailed examination	The analysis showed that the water contained toxic substances.
The plural is analyses, /əˈnæləsiz/. Word family: analyze the verb, analyst the person, analytical the adjective. It takes of for the thing studied: an analysis of the data. Uncountable in careful analysis, countable in three separate analyses.
trialneutral /ˈtraɪəl/ A test of something new to see if it works and is safe. Synonyms: test	test of something new	The new drug is still in trials, so it is not available yet.
A trial tests something on people over time, while an experiment is a single controlled test, which is why drugs go through trials and physics runs experiments. The fixed phrases are in trials and, in a court, on trial. Trial and error is a set phrase.
clinical trialneutral /ˈklɪnɪkəl ˈtraɪəl/ A scientific test of a new medicine on people to check that it is safe. Synonyms: drug trial, medical study, clinical study	medical test on people	The clinical trial involved more than a thousand volunteers.
You run or conduct a clinical trial and you enroll people in one. Trials are usually described by stage, as in a phase three clinical trial, and are often randomized and controlled, which is what the abbreviation RCT stands for.
conclusionneutral /kənˈkluʒən/ The final decision or judgement after thinking about all the facts. Synonyms: judgment, inference, verdict	final judgment	The team reached the conclusion that more data was needed.
You reach, draw or come to a conclusion; you do not make one. Jump to conclusions means decide too quickly. In conclusion signals the last paragraph of an essay. A conclusion is your interpretation; a finding is the raw result.
journal (academic)formal /ˈdʒɜrnəl/ A serious magazine where scientists publish their research articles. Synonyms: periodical, academic publication, review	research periodical	Her article was accepted by one of the best medical journals.
In this sense a journal prints articles checked by other experts, so you publish in a journal, never publish on one. Countable. The same word also means a private diary, and journalism is separate work for newspapers.
variableneutral /ˈvɛriəbəl/ Something that can change and that scientists control in an experiment. Synonyms: factor, measure, condition	changing measured quantity	In this experiment, temperature is the only variable we change.
The independent variable is the one you change and the dependent variable the one you measure. Control for a variable means hold it steady. As an adjective it means changeable: variable weather, variable results.
factorneutral /ˈfæktər/ One of the things that influences a result or situation. Synonyms: element,cause	an influencing element	Age is an important factor in how quickly the body recovers.
A factor in the decision, the factors behind the rise: those are the two prepositions. Common with key, major, contributing and risk. A factor helps produce a result, while a cause produces it directly.
phenomenonformal /fəˈnɑməˌnɑn/ Something that happens in nature or society, especially something studied by science. Synonyms: occurrence, event, observed fact	an observed occurrence	Lightning is a natural phenomenon that scientists understand quite well.
The plural is phenomena, /fəˈnɑmənə/, and a phenomena is a very common error. Frequent with natural, global, recent and widespread. The word is neutral in science, so a phenomenon is simply something observed, not something amazing.
control groupneutral /kənˈtroʊl ˌɡrup/ The group in an experiment that does not receive the thing being tested. Synonyms: comparison group, baseline group, placebo group	untreated comparison group	The control group was given a placebo instead of the real medicine.
The other side of the comparison is the treatment or experimental group, and the usual frame is compared with the control group. With no control group there is nothing to compare against, which is why such studies are called weak.
participantneutral /pɑrˈtɪsəpənt/ A person who takes part in a study, activity, or event. Synonyms: subject, volunteer, respondent	person taking part	All the participants were asked to sign a consent form.
Countable, and it takes in: participants in the study. It is the standard word in research writing, where subject now sounds older and colder. The verb is participate in something, never participate something.
ethicsformal /ˈɛθɪks/ Ideas about what is morally right and wrong in an activity. Synonyms: morals, moral principles, moral standards	standards of right conduct	The committee discussed the ethics of testing new drugs on animals.
Plural in form but singular in meaning when it names the field: medical ethics is a huge subject. Plural when it means one person's standards: her ethics were questioned. Ethics committee and the adjective ethical are both very common.
fundingneutral /ˈfʌndɪŋ/ Money given for a special purpose such as research. Synonyms: financing, financial support, grants	money for a project	The project lost its funding after the first disappointing results.
Uncountable, so no fundings and no a funding; use funds or grants when you need a countable word. You apply for, receive, secure, cut or lose funding. Common with public, government and research.
limitationneutral /ˌlɪməˈteɪʃən/ A weak point that makes something less good or less complete. Synonyms: weakness	weakness; shortcoming	Every study has limitations that the authors should mention clearly.
Keep it apart from limit, the point you may not pass, which gives a speed limit and never a speed limitation. Usually plural in research writing: the limitations of the study. Naming them is expected in a paper, not an admission of failure.
probabilityneutral /ˌprɑbəˈbɪləti/ How likely it is that something will happen or be true. Synonyms: likelihood, odds	likelihood; chance	There is a high probability that the results are correct.
The patterns are the probability of plus a noun or -ing form, and probability that plus a clause. In all probability means almost certainly. Uncountable in general use, but countable for a stated figure: a probability of 0.05.
techniqueneutral /tɛkˈnik/ A special way of doing something that needs skill or knowledge. Synonyms: method	skilled way of doing something	This technique allows doctors to detect the disease much earlier.
Countable, and it takes for: a technique for measuring blood flow. A technique is the specific skill; a method is the broader plan. Also used of art, music and sport, where it means physical execution rather than ideas.
procedureformal /prəˈsidʒər/ The official or correct way of doing something, step by step. Synonyms: process, protocol, routine	set sequence of steps	The safety procedure must be followed at all times in the lab.
Countable, and it takes for: the procedure for reporting an accident. You follow a procedure, and standard procedure is a fixed phrase. In hospitals a procedure is an operation, so a minor procedure still means surgery.
advance (noun)neutral /ədˈvæns/ An improvement or new development in an area of knowledge. Synonyms: development,improvement	step forward; improvement	Recent advances in medicine have doubled survival rates for some cancers.
Usually plural and followed by in for the field: advances in medicine, technological advances. In advance is a separate sense meaning beforehand, as in book in advance.
to proveneutral /pruv/ To show that something is definitely true using facts. Synonyms: to demonstrate,to show	show to be true	The results prove that the old theory was wrong.
Past tense proved; both proved and proven work as the participle, but proven is the usual adjective, as in proven results. Prove that plus a clause is the common frame. In science evidence normally supports a claim, so prove is a strong word.
to conductformal /kənˈdʌkt/ To organize and do something such as a study or an experiment. Synonyms: to carry out,to do	carry out; organize	The study was conducted over a period of five years.
Stress differs by part of speech: the verb is /kənˈdʌkt/ while the noun conduct, meaning behavior, is /ˈkɑndʌkt/. It goes with a study, a survey, research, an interview and an experiment, and is often passive: the study was conducted in 2019.
to observeneutral /əbˈzɜrv/ To watch something carefully, especially to learn something. Synonyms: to watch,to notice	watch closely	The team observed how the cells reacted to the new substance.
Before another verb there is no to: we observed the cells divide or dividing. It also takes a plain object or a that clause: observe the cells, observe that levels fell. A formal second sense means to remark, and observe a rule means obey it.
to analyzeneutral /ˈænəˌlaɪz/ To study something carefully in order to understand it or explain it. Synonyms: to examine,to study	examine in detail	The data was analyzed using a special computer program.
American English spells this analyze; analyse is the British form, while the noun is analysis in both. The past is analyzed and the person an analyst. You analyze data, results or a sample, and add for to name what you seek: analyzed for lead.
to investigateneutral /ɪnˈvɛstəˌɡeɪt/ To try to find out the facts about something in a careful way. Synonyms: to examine,to study	look into; examine	Scientists are investigating why the bees are disappearing so quickly.
Takes a direct object with no preposition: investigate the cause, never investigate into it. Often followed by whether, why or how plus a clause. It is also the standard verb for police work, so context separates research from crime.
to testneutral /tɛst/ To use or examine something to find out if it works correctly. Synonyms: to try,to check	check by trying	The vaccine was tested on thousands of volunteers before being approved.
You test something on people or animals, and you test for whatever you are looking for: tested for the virus. Test positive and test negative are fixed. The noun and verb are the same word, and tried and tested means proven reliable.
to demonstrateformal /ˈdɛmənˌstreɪt/ To show clearly that something is true or how something works. Synonyms: to show,to prove	show clearly	The experiment demonstrates that light behaves like a wave.
Demonstrate that plus a clause is the usual research frame, and you can demonstrate a method to someone. A second sense is to march in protest, which gives demonstration and demonstrator. The adjective demonstrable means provable.
to confirmneutral /kənˈfɜrm/ To show or say that something is definitely true. Synonyms: to verify,to prove	show to be correct	Further studies are needed to confirm these early results.
Confirm that plus a clause, or confirm plus a noun: confirm the results. It assumes an earlier claim, so you cannot confirm something nobody has suggested. Common with independently, later and further studies.
to concludeformal /kənˈklud/ To decide that something is true after looking at all the information. Synonyms: determine, infer, deduce	decide after weighing facts	The authors concluded that the drug had no serious side effects.
Conclude that plus a clause is the research frame, and the that is usually kept in writing. A second sense is simply to finish: the talk concluded at six. The noun is conclusion, and conclusive means settling the matter for good.
to publishneutral /ˈpʌblɪʃ/ To print or make information available for people to read. Synonyms: release, issue	make public in print	The results will be published once they have been checked by other experts.
You publish in a journal and publish on a topic, and a press publishes an author. The passive is very common: the results were published last year. Publish or perish describes academic pressure. The noun is publication.
to identifyneutral /aɪˈdɛntəˌfaɪ/ To recognize something and say exactly what it is. Synonyms: to recognize, to pinpoint	recognize and name	Researchers have identified the gene responsible for the disease.
The frame is identify something as something: the powder was identified as arsenic. Identify with means feel a connection to, a quite different sense. The noun is identification, shortened to ID in everyday use.
to classifyneutral /ˈklæsəˌfaɪ/ To put things into groups according to their type. Synonyms: to categorize, to group	sort into groups	Biologists classify living things into large groups called kingdoms.
Classify something as or into: classified as endangered, classified into three groups. The noun is classification. A second sense concerns official secrecy, so classified documents means secret ones rather than sorted ones.
to verifyformal /ˈvɛrəˌfaɪ/ To check that something is true or correct. Synonyms: to check,to confirm	check for correctness	The figures were verified by an independent team of experts.
Verify means check that something is accurate; confirm means state that it is true. You verify data, figures, a claim or an identity, and verify that plus a clause also works. The noun is verification and the adjective verifiable.
to discoverneutral /dɪˈskʌvər/ To find something that existed but was not known before. Synonyms: to find	find something unknown	Penicillin was discovered by accident in 1928.
You discover what already existed and invent what did not. Discover that plus a clause is common: we discovered that the sample was contaminated. Often passive with by: discovered by accident. The noun is discovery.
to estimateneutral /ˈɛstəˌmeɪt/ To guess an amount or value using the information you have. Synonyms: to calculate,to guess	work out approximately	Experts estimate that the planet has warmed by more than one degree.
The verb ends in /eɪt/ while the noun estimate ends in /ət/, /ˈɛstəmət/. Estimate that plus a clause, or estimate plus a figure. It is a calculation from evidence, so it is more careful than a guess.
to monitorneutral /ˈmɑnətər/ To watch and check something carefully over a period of time. Synonyms: to watch,to check	keep checking over time	The volunteers were monitored for six months after taking the drug.
It implies repeated checking over a period, not one look: monitored for six months. Often passive, as in patients were closely monitored, and common with carefully and continuously. The noun monitor is both a screen and a person who watches.
scientificneutral /ˌsaɪənˈtɪfɪk/ Connected with science or using the methods of science. Synonyms: empirical, evidence-based, systematic	based on science	There is no scientific evidence to support this popular belief.
This is the adjective belonging to science: scientific evidence, scientific method, the scientific community. Use scientific, not science, before those nouns. The adverb scientifically means by scientific means: scientifically proven.
validneutral /ˈvæləd/ Based on good reasons or facts and therefore acceptable. Synonyms: sound, well-founded, legitimate	sound; well founded	The results are only valid if the sample is large enough.
Valid goes with point, argument, reason and criticism, and in research with results and measures. A second sense is still usable in time: a valid passport. The opposite adjective invalid is stressed on the second syllable, /ɪnˈvæləd/.
innovativeneutral /ˈɪnəˌveɪtɪv/ Using new ideas or methods that did not exist before. Synonyms: original,creative	new and original	The company has developed an innovative way to store solar energy.
The word is approving, so an innovative solution is praise, while novel is neutral and only says new. Often with highly or truly, and the family is innovate, innovation, innovator. Stress falls on the first syllable in American English.
theoreticalneutral /ˌθiəˈrɛtɪkəl/ Based on ideas rather than on practice or experiments. Synonyms: abstract, conceptual, untested	in ideas, not practice	The idea is still theoretical because nobody has tested it in practice.
It contrasts with practical, applied or experimental: theoretical physics beside applied physics. The adverb theoretically often means in principle but perhaps not in reality. Theoretical describes ideas; hypothetical describes an imagined case.
randomneutral /ˈrændəm/ Happening or chosen by chance, without any plan or pattern. Synonyms: chance, unplanned	chosen by chance	The participants were chosen at random from a much larger group.
At random and randomly are the usual adverbs, and random sampling and randomized trial are fixed research terms. It means having no pattern, not merely unplanned. In casual speech random can also mean odd: a random question.
complexneutral /kəmˈplɛks/ Made of many connected parts and difficult to understand. Synonyms: complicated	intricate; many-parted	The human brain is far more complex than any computer ever built.
Complex means having many connected parts, while complicated stresses that something is hard to deal with. The adjective is usually stressed on the second syllable, but the noun complex, a group of buildings, takes first-syllable stress. The noun complexity is uncountable.
in theoryneutral /ɪn ˈθiəri/ Used to say what should happen if the ideas about it are correct. Synonyms: in principle, on paper	in principle; supposedly	In theory, the machine can work for ten years without any repairs.
It sets up a contrast, so a but nearly always follows, and the natural partner phrase is in practice. Normally at the front of a sentence with a comma after it, with no article and no plural.
trial and errorneutral /ˌtraɪəl ənd ˈɛrər/ Trying different ways and learning from mistakes until something works. Synonyms: experimentation, repeated testing, learning by doing	learning by repeated attempts	The inventors found the right design through trial and error.
Normally after by or through: learned by trial and error. Never add an s to error, and never an article to either noun. It can also stand before a noun as a modifier, as in a trial and error approach.
margin of errorneutral /ˌmɑrdʒən əv ˈɛrər/ The amount by which a measurement or result may not be exact. Synonyms: tolerance, error range, allowance for error	allowed range of inaccuracy	The poll has a margin of error of three per cent.
It says how far a figure may be out, so a difference smaller than the margin of error may not be a real difference at all. The frame is a margin of error of three percent, nearly always singular, and common with small, wide and narrow.
dataneutral /ˈdeɪtə/ Facts, numbers, or information collected and used to study something. Synonyms: information,figures	collected facts and figures	The data was collected over ten years and is still being analyzed.
Treated as uncountable in modern American usage, so the data shows and this data, though strict scientific style still writes the data show. The singular datum is now rare. You collect, gather, analyze and store data, and you have data on a subject.
statisticsneutral /stəˈtɪstɪks/ A collection of numbers that gives information about something. Synonyms: figures,data	numerical information	The latest statistics show a clear fall in infection rates.
Plural when it means figures: the statistics show. Singular when it names the subject: statistics is difficult. One figure is a statistic. The short form stats is informal, and statistically significant is a fixed technical phrase.
graphneutral /ɡræf/ A drawing that uses lines or bars to show how numbers change. Synonyms: chart,diagram	chart of changing numbers	The graph shows how global temperatures have risen since 1900.
You plot or draw a graph, and a graph shows or indicates a pattern. Use a graph of what is measured, and on the graph for a position. Bar graph and line graph are the usual types, while chart is the broader everyday word.
percentageneutral /pərˈsɛntɪdʒ/ An amount expressed as a part of a hundred. Synonyms: proportion, share, fraction	proportion per hundred	Only a small percentage of the samples contained harmful bacteria.
Use percentage with a describing word and no number: a large percentage, a small percentage of the samples. With an actual number use percent instead: ten percent. After a percentage of, the verb follows the noun, so a small percentage of samples were damaged.
rateneutral /reɪt/ A measurement of how often something happens or how fast it changes. Synonyms: speed,level	how often or how fast	The success rate of the new operation is above ninety per cent.
Very productive as the second half of a compound: birth rate, success rate, heart rate, crime rate. Rates rise, fall or hold steady, and at a rate of takes a figure. At any rate is an unrelated phrase meaning anyway.
equationneutral /ɪˈkweɪʒən/ A mathematical statement showing that two amounts are equal. Synonyms: formula, mathematical statement, expression	mathematical statement of equality	Even a simple equation can describe a very complex movement.
You solve, write or balance an equation. Its middle consonant is the zh sound of vision, and the stress falls on that second syllable. The related verb equate takes with or to, as in equate size with strength.
formulaneutral /ˈfɔrmjələ/ Letters, numbers, or symbols that show a scientific rule or fact. Synonyms: rule, set expression, recipe	rule written in symbols	The chemical formula for water is H2O, as everyone learns at school.
The plural is formulas in general use and formulae, /ˈfɔrmjəli/, in mathematics and science. Formula for plus a result or product: a formula for success. A separate everyday sense is prepared milk for babies.
trendneutral /trɛnd/ A general direction in which a situation is changing or developing. Synonyms: tendency,pattern	general direction of change	There is a worrying upward trend in global energy consumption.
A trend in prices but a trend toward later marriage: in names the field, toward the direction. Trends are upward, downward, rising, clear or worrying. The verb trend and the adjective trendy belong to fashion and social media, not to data.
unitneutral /ˈjunɪt/ A standard amount used for measuring something. Synonyms: measure, standard measure, quantity	standard measuring amount	The meter is the basic unit of length in the scientific system.
The pattern is a unit of plus what is measured: a unit of length, a unit of energy, and SI units are the agreed scientific set. The word also covers a part of a machine, a section of a course and a hospital department.
satelliteneutral /ˈsætəˌlaɪt/ A machine sent into space that travels around the Earth. Synonyms: orbiter, spacecraft, probe	object orbiting a planet	The satellite was launched into orbit to monitor weather patterns.
A satellite is launched or placed into orbit, and then it orbits the Earth with no preposition at all. A natural satellite is a moon; an artificial one is a machine. Before a noun it means delivered from space: satellite images, satellite phone.
rocketneutral /ˈrɑkɪt/ A vehicle shaped like a long tube that travels into space. Synonyms: launch vehicle, launcher, spacecraft	spacecraft launch vehicle	The rocket will carry three astronauts to the space station next month.
A rocket is launched, lifts off and carries a crew or a payload. It is not rocket science is a common way of saying something is easy. The verb rocket means rise very fast, as in prices rocketed last year.
astronautneutral /ˈæstrəˌnɔt/ A person who travels into space in a spacecraft. Synonyms: cosmonaut, space traveler, crew member	space traveler	The first astronaut who walked on the Moon became famous all over the world.
Astronaut is the standard English term, while a Russian one is called a cosmonaut. The astro part means star and links the word to astronomy and astrophysics; astrology, which reads star signs, is not a science despite the similar look.
telescopeneutral /ˈtɛləˌskoʊp/ An instrument that makes distant objects such as stars look bigger. Synonyms: optical instrument, scope	instrument for seeing far	Thanks to this telescope, astronomers can see galaxies that are billions of years old.
You look through a telescope rather than into one, and you point or aim it at something. Space telescope and radio telescope are the common types. A microscope does the opposite job, enlarging very small things.
galaxyneutral /ˈɡæləksi/ A very large group of stars held together in space. Synonyms: star system, stellar system, cluster of stars	huge system of stars	Our galaxy contains more stars than anyone can count.
Ours is the Milky Way, written with capitals, while our galaxy keeps a small g. The plural is galaxies. In loose everyday use a galaxy of means a dazzling collection of people: a galaxy of talent.
universeneutral /ˈjunəˌvɜrs/ All of space and everything that exists in it. Synonyms: cosmos	all of existence	Scientists believe the universe has been expanding since it began.
Almost always singular and with the: the universe began. The adjective universal usually means shared by everyone rather than cosmic, as in universal agreement. Cosmos is a close equivalent with a more literary feel.
solar systemneutral /ˈsoʊlər ˈsɪstəm/ The Sun and all the planets that move around it. Synonyms: planetary system, star system, the Sun's family	the Sun and its planets	Jupiter is the largest planet in our solar system.
Normally with the and in lower case when ours is meant. Solar means of the Sun, which gives solar energy, solar panel and solar eclipse. A similar system around another star is called a planetary system.
orbitneutral /ˈɔrbɪt/ The curved path of an object moving around a planet or star. Synonyms: circular path, revolution, trajectory	path around a body	The satellite remains in orbit around the Earth for about fifteen years.
A thing is in orbit around something, goes into orbit, and orbits the planet with no preposition at all. The same form serves as noun and verb. The adjective is orbital, and a figurative orbit is someone's area of influence.
to collideneutral /kəˈlaɪd/ To hit something or someone with great force while moving. Synonyms: to crash,to hit	crash into	Scientists believe a huge asteroid collided with the Earth millions of years ago.
Collide with something, or two things collide with each other; with a plural subject no object is needed, as in two cars collided. It suits two moving things best, so a car hits a wall but two cars collide. The noun is collision, not colliding.
missionneutral /ˈmɪʃən/ An important journey or task, especially one into space. Synonyms: expedition, operation, assignment	assigned important task	The mission was canceled because of a technical problem.
A mission to Mars: to names the destination. Missions are launched, carried out, completed, aborted or canceled, and on a mission means currently doing one. A mission statement is a company's declared purpose.
atmosphereneutral /ˈætməsˌfɪr/ The layer of gases around the Earth or another planet. Synonyms: air, air layer, gas envelope	layer of surrounding gases	The Earth's atmosphere protects us from dangerous radiation.
The adjective is atmospheric, and the physical sense almost always carries the: the Earth's atmosphere. A second, uncountable sense is the mood of a place, as when a restaurant has a pleasant atmosphere.
gravityneutral /ˈɡrævəti/ The force that pulls objects towards the Earth. Synonyms: gravitational pull, gravitational force, attraction	downward pulling force	Objects fall to the ground because gravity pulls them towards the Earth.
Zero gravity, center of gravity and the force of gravity are the fixed phrases, and the bare noun takes no article: gravity pulls. A separate sense is seriousness, as in the gravity of the situation. The adjective is gravitational.
astronomerneutral /əˈstrɑnəmər/ A scientist who studies the stars, planets, and space. Synonyms: space scientist, astrophysicist, stargazer	scientist who studies space	Astronomers have discovered thousands of planets outside our solar system.
An astrologer, who reads star signs, is something else entirely. The field is astronomy and the adjective astronomical, which in everyday speech simply means enormous: an astronomical price. Stress falls on the second syllable.
radiationneutral /ˌreɪdiˈeɪʃən/ A form of energy that can be dangerous in large amounts. Synonyms: rays, radiant energy, emitted energy	energy given off as rays	Workers at the plant are protected from radiation by special clothing.
You are exposed to radiation and protected from it, and levels of radiation rise or fall. It is uncountable, so never a radiation. The verb radiate and the noun radiator belong to heat, and in hospitals radiation also names a cancer treatment.
atomneutral /ˈætəm/ The smallest unit of a chemical element. Synonyms: basic unit, smallest unit, particle	smallest unit of an element	Everything around us is made up of atoms too small to see.
An atom is the smallest piece of an element, not the smallest thing there is: atoms are themselves built from electrons, protons and neutrons. The adjective is atomic, which moves the stress to the second syllable, as in atomic energy.
particleneutral /ˈpɑrtɪkəl/ An extremely small piece of matter. Synonyms: speck, fragment, tiny piece	tiny piece of matter	These particles are so small that no normal microscope can show them.
Common with tiny, fine, charged, dust and subatomic, and particle physics is the branch that studies the smallest ones. In grammar the same word names a small function word, such as the to of an infinitive.
moleculeneutral /ˈmɑləˌkjul/ The smallest unit of a substance, made of two or more atoms. Synonyms: chemical unit, compound unit, particle	group of joined atoms	A water molecule is formed when two hydrogen atoms join one oxygen atom.
The pattern is a molecule of plus the substance: a molecule of water. The adjective molecular shifts the stress to the second syllable, /məˈlɛkjələr/, as in molecular biology.
frequencyneutral /ˈfrikwənsi/ The number of times a wave repeats itself each second. Synonyms: rate of repetition, recurrence, cycle rate	rate of repetition	Radio stations broadcast at different frequencies so that they do not interfere with each other.
High frequency and low frequency are fixed, a radio broadcasts on a frequency, and the frequency of earthquakes means how often they happen. That second sense is uncountable, while a measured value is countable.
frictionneutral /ˈfrɪkʃən/ The force that slows objects when they rub against each other. Synonyms: resistance, drag, rubbing force	resistance between surfaces	Friction between the tires and the road allows the car to stop safely.
Friction between the tire and the road: between is the preposition, and the noun is uncountable. It always works against motion, which is why it slows things down and produces heat. A common figurative sense is tension between people.
magneticneutral /mæɡˈnɛtɪk/ Having the power to attract metals such as iron. Synonyms: magnetized, of a magnet, iron-attracting	able to attract iron	The Earth has a magnetic field that protects it from particles coming from the Sun.
Magnetic field, magnetic north and magnetic resonance are the fixed combinations. The noun is a magnet and the study of it is magnetism, so do not use magnetic as a noun. Used of a person it means strongly attractive: a magnetic personality.
pressureneutral /ˈprɛʃər/ The force produced when something presses against something else. Synonyms: force, compression, push	force on a surface	As you go deeper under water, the pressure increases quickly.
Blood pressure, air pressure and high pressure are fixed phrases, and pressure rises or falls. A second sense is being pushed to act, giving put pressure on someone and pressure someone to agree. Uncountable either way.
massneutral /mæs/ The amount of matter that an object contains. Synonyms: quantity of matter, amount of matter, bulk	quantity of matter	The mass of an object does not change when you take it to the Moon.
Mass is not weight: mass stays the same while weight depends on gravity, and in physics it is uncountable. A mass of something means a large amount. Before a noun it means large-scale: mass production, mass extinction.
speed of lightneutral /ˌspid əv ˈlaɪt/ The speed at which light moves, the fastest speed possible. Synonyms: light speed, velocity of light, the universal speed limit	light's fixed maximum speed	Nothing in the universe can travel faster than the speed of light.
It names one exact constant in a vacuum, so at the speed of light means that precise figure rather than simply very fast. Common with at, faster than and close to, always with the and never plural.
energyneutral /ˈɛnərdʒi/ The power that makes things work, move, or live. Synonyms: power	power; capacity for work	The Sun provides the energy that almost all living things depend on.
Uncountable in physics and in the fuel sense: solar energy, energy consumption. Countable only when you mean kinds, as in renewable energies. In physics it is the capacity to do work and is measured in joules, not felt as liveliness.
cellneutral /sɛl/ The smallest living part of an animal or a plant. Synonyms: living unit, biological unit, basic unit	basic unit of life	The human body is made up of billions of cells that are constantly being replaced.
Cells divide, grow and die, and the adjective is cellular. Several unrelated senses share the spelling: a prison cell, a battery cell, a spreadsheet cell, and cell phone, where cell refers to an area of the network.
geneneutral /dʒin/ The part of a cell that controls which qualities parents pass to children. Synonyms: hereditary unit, genetic unit, DNA segment	unit of inheritance	This gene is passed from parents to children through generations.
A gene is for something: the gene for eye color. Genes are inherited, passed on, carried and expressed. The word is pronounced exactly like jean, the adjective is genetic and the field is genetics.
DNAneutral /ˌdi ɛn ˈeɪ/ The chemical in cells that carries genetic information. Synonyms: genetic material, genetic code, hereditary material	genetic material	The scientists compared the DNA of the two animals to see how closely they were related.
Uncountable, always capitalized, and spoken as three letters with the stress on the last. No article in general statements: DNA carries information. A DNA test and DNA evidence are fixed. Figuratively it means core identity: care is in our DNA.
geneticneutral /dʒəˈnɛtɪk/ Connected with the genes that parents pass to their children. Synonyms: inherited, hereditary, inborn	inherited; of the genes	Some diseases have a genetic origin, so they run in families.
Genetic means carried in the genes, while hereditary means passed down within a family. Genetic code, genetic disorder and genetic engineering are the fixed combinations. It is an adjective only: the noun is a gene and the field genetics.
genetically modifiedneutral /dʒəˈnɛtɪkli ˈmɑdəˌfaɪd/ Changed by scientists so that a plant or animal has new qualities. Synonyms: GM, engineered, bioengineered	altered by gene technology	Genetically modified crops are grown in many countries despite public concern.
Keep the adverb whole: genetic modified is an error, genetically modified is right. It sits before its noun and is usually shortened to GM, as in GM crops. The matching noun phrase is genetic modification.
organismformal /ˈɔrɡəˌnɪzəm/ A living thing, especially a very small one. Synonyms: living thing, creature, life form	a living thing	Even the simplest organisms can adapt to changes in their environment.
Keep three lookalikes apart: an organism is a whole living thing, an organ is one part of a body, and organic on a food label means grown without synthetic chemicals. Common pairings are living, simple, single-celled and microscopic organism.
speciesneutral /ˈspiʃiz/ A group of animals or plants of the same type. Synonyms: kind, type, biological group	one kind of organism	This species is found only in the mountains of northern Spain.
The same form in singular and plural: one species, many species, never a specie. The verb follows the meaning, so this species is rare but these species are rare. Common with endangered, native, invasive and new.
evolutionneutral /ˌɛvəˈluʃən/ The slow change of living things over millions of years. Synonyms: gradual development, gradual change, descent with modification	gradual development over time	Darwin's theory of evolution explains how species change over long periods of time.
In biology it describes change across generations of a population, not change inside one individual's lifetime. Uncountable and usually followed by of: the evolution of language. The adjective is evolutionary and the verb evolve.
to evolveneutral /ɪˈvɑlv/ To change and develop slowly over a long time. Synonyms: develop, change gradually, grow	develop slowly	Birds are believed to have evolved from dinosaurs millions of years ago.
It takes from for the origin and into for the outcome: evolved from earlier forms, evolved into a new species. Normally there is no object at all: species evolve, plans evolve. Because it implies slow change, it does not suit a sudden switch.
to adaptneutral /əˈdæpt/ To change your behavior or body to suit a new situation. Synonyms: to adjust	adjust to new conditions	Animals that cannot adapt to a changing climate risk dying out.
Adapt to something when you adjust, and adapt something for a new purpose: the novel was adapted for film. Do not confuse it with adopt, which means take up or take on. The noun is adaptation.
bacterianeutral /bækˈtɪriə/ Very small living things, some of which cause disease. Synonyms: germs, microbes, microorganisms	single-celled microbes	Some bacteria are becoming resistant to the antibiotics we use most often.
Plural in form, with the rare singular bacterium, so write bacteria are rather than bacteria is. Bacteria are not viruses, which are far smaller and need a host cell. The adjective is bacterial, as in a bacterial infection.
habitatneutral /ˈhæbəˌtæt/ The natural place where an animal or plant lives. Synonyms: natural home, natural environment, range	natural living place	The natural habitat of these birds is being destroyed by farming.
A habitat is where one species lives, an environment is the whole set of surroundings, and an ecosystem is the community of living things plus those surroundings. Habitats are destroyed, lost, protected and restored; natural habitat is the commonest pair.
ecosystemneutral /ˈɛkoʊˌsɪstəm/ All the living things in an area and how they affect each other. Synonyms: biological community, biome, natural system	living community and surroundings	A small change in temperature can damage an entire ecosystem.
It covers the living things together with their physical surroundings, which is what separates it from a habitat. Described as whole, fragile, marine or forest. It is now common in business too: a startup ecosystem.
biodiversityformal /ˌbaɪoʊdəˈvɜrsəti/ The variety of plants and animals living in a place. Synonyms: biological diversity, species variety, variety of life	variety of living things	Protecting biodiversity has become one of the greatest challenges of our time.
It measures the range of different species present, not the number of individual animals. You protect, conserve, lose or threaten it, and biodiversity loss is the standard phrase. Uncountable, so no a biodiversity and no plural.
extinctneutral /ɪkˈstɪŋkt/ No longer existing as a living species. Synonyms: died out, wiped out, no longer surviving	no longer existing	Many species will become extinct unless we protect their habitats.
An adjective used with be, become or go: the species went extinct. It applies to a whole species, never to one animal, so a dead bird is not extinct. The noun is extinction, and endangered names the stage before it.
mutationformal /mjuˈteɪʃən/ A change in the genes of a living thing. Synonyms: genetic change, alteration, variant	change in a gene	A single mutation in a gene can sometimes cause a serious disease.
A mutation in a gene: in is the preposition. Mutations arise, occur or are inherited, and the word is neutral in biology, so a mutation may be harmful, harmless or useful. The verb is mutate and the adjective mutant.
test tubeneutral /ˈtɛst ˌtub/ A thin glass tube used in a laboratory for experiments. Synonyms: sample tube, glass tube, vial	narrow laboratory tube	The chemist heated the liquid in a test tube.
You put a sample in a test tube and stand it in a rack. It is not a beaker, which is wide and open at the top. Two words as a noun but hyphenated before another noun: a test-tube baby.
immune systemneutral /ɪˈmjun ˌsɪstəm/ The parts of the body that fight illness and infection. Synonyms: bodily defenses, defense system, immune defenses	the body's natural defenses	A healthy diet helps the immune system fight infections.
It is strengthened, weakened or suppressed, and it fights off infection. Nearly always singular with the or a possessive: your immune system. The adjective immune takes to: immune to measles.
to reactneutral /riˈækt/ To change when mixed with another substance, or to respond to something. Synonyms: respond, answer, act in response	respond; change chemically	The metal reacts with oxygen and turns brown.
React to a situation, react with a substance, and react against something you oppose. In chemistry two substances react with each other to form something new. The noun is reaction and the adjective reactive.
to simulateneutral /ˈsɪmjəˌleɪt/ To use a model or computer to copy how something works in real life. Synonyms: model, replicate, imitate	imitate with a model	The software simulates how the bridge behaves in strong wind.
Takes a direct object: simulate a crash, simulate real conditions. The noun simulation is countable and a simulator is the machine. It means copy in order to study, so a simulated test is deliberate rather than dishonest.
stem cellneutral /ˈstɛm ˌsɛl/ A basic cell that can grow into many different types of cell. Synonyms: undifferentiated cell, precursor cell, progenitor cell	undeveloped versatile cell	Stem cells can develop into almost any type of cell in the body.
Two words, countable, and usually plural: stem cells. Before a noun the pair works as a modifier: stem cell research, stem cell therapy. The stem part points to the further growth these cells can still produce.
life expectancyneutral /ˈlaɪf ɪkˌspɛktənsi/ The number of years that a person is expected to live. Synonyms: average lifespan, expected lifespan, longevity	expected lifespan	Life expectancy has risen sharply thanks to advances in medical research.
It is an average across a population, so it predicts nothing certain about one person. It rises, falls or increases, and appears with of or a possessive: life expectancy at birth, the country's life expectancy.
food chainneutral /ˈfud ˌtʃeɪn/ The natural system in which each living thing eats another. Synonyms: food web, feeding order, trophic chain	eating order in nature	If small fish disappear, the whole food chain is affected.
Up and down are the normal directions: higher up the food chain, usually with the. Figuratively it means rank inside an organization. A food web is the wider version, with many branching links.
softwareneutral /ˈsɔftˌwɛr/ The programs that make a computer or phone work. Synonyms: programs	computer programs	The company is developing software that translates speech in real time.
Uncountable, so never a software or softwares; say a piece of software, a program or an app. It combines freely: software company, software update, software engineer. You run, install and update software.
hardwareneutral /ˈhɑrdˌwɛr/ The physical parts of a computer, not the programs. Synonyms: equipment, physical components, machinery	physical computer equipment	You do not need to buy new hardware to run this program.
Uncountable like software, so say a piece of hardware. An older sense is still alive in American English, which is why a hardware store sells hammers and screws rather than laptops.
artificial intelligenceneutral /ˌɑrtəˈfɪʃəl ɪnˈtɛlədʒəns/ Computer systems that can do tasks that normally need human thinking. Synonyms: AI	machine intelligence	Artificial intelligence is already being used to detect diseases earlier than doctors can.
Uncountable and usually shortened to AI, spoken as two letters. No article in general statements: artificial intelligence is changing medicine. Before a noun the short form is normal: AI tools, AI models.
machine learningneutral /məˈʃin ˈlɜrnɪŋ/ A way for computers to learn from data instead of following fixed rules. Synonyms: statistical learning, data-driven learning, ML	learning from data	Machine learning allows computers to improve without being programmed for every task.
Uncountable, often shortened to ML, and singular: machine learning has improved quickly. It is one branch of artificial intelligence rather than another name for it. As a modifier: a machine learning model.
algorithmneutral /ˈælɡəˌrɪðəm/ A set of steps that a computer follows to solve a problem. Synonyms: procedure, set of rules, computational recipe	step-by-step procedure	The algorithm decides which videos each user sees first.
Watch the spelling: the ending is rithm, with no y and no e. Algorithms are written, trained, tuned and applied, and the adjective is algorithmic. Said with the, the algorithm now loosely means whatever decides what a platform shows you.
robotneutral /ˈroʊˌbɑt/ A machine that can do work by itself, often controlled by a computer. Synonyms: automaton, machine, android	automatic working machine	Robots are increasingly used in factories where the work is repetitive or dangerous.
Countable and stressed on the first syllable. The adjective is robotic and the field robotics, which takes a singular verb. Common pairings: robot arm, industrial robot, robot vacuum.
automationneutral /ˌɔtəˈmeɪʃən/ The use of machines to do work that people did before. Synonyms: mechanization, computerization, automatic operation	replacing work with machines	Automation has replaced many jobs that people used to do by hand.
Automation is introduced, increased or resisted, and it combines as factory automation and home automation. It is uncountable, so no an automation. The verb is automate and the adjective automated, as in an automated process.
sensorneutral /ˈsɛnsər/ A small piece of equipment that notices light, heat, or movement. Synonyms: detector, probe, gauge	detecting device	A sensor turns the lights off automatically when nobody is in the room.
Named after what it detects: a motion sensor, a temperature sensor. Sensors detect, measure and trigger. Watch the spelling against censor, a person who removes objectionable content.
circuitneutral /ˈsɜrkɪt/ The complete path that electricity follows. Synonyms: electrical loop, electrical path, loop	closed electrical path	If the circuit is broken at any point, the electricity stops flowing.
A circuit is complete, closed, open or broken, and a short circuit is a fault. The first syllable sounds like sir. Other senses include a fixed route and a series of events: the tennis circuit.
wirelessneutral /ˈwaɪərləs/ Working without cables, using radio signals instead. Synonyms: cordless, cable-free, over-the-air	working without cables	The office uses a wireless connection, so there are no cables under the desks.
Chiefly an adjective today: a wireless connection, wireless headphones. Wi-Fi names one specific technology and keeps its hyphen and capitals. The old noun sense meaning a radio set now sounds dated.
digitalneutral /ˈdɪdʒətəl/ Using computer technology that stores information as numbers. Synonyms: computerized, electronic, numeric	computer-based; stored as numbers	Most of our photos now exist only in digital form.
Its opposite here is analog, spelled without the ue in American English. It sits before a noun: digital camera, digital copy, digital skills. Digital also means of the fingers, which is where the word came from.
electronicneutral /ɪˌlɛkˈtrɑnɪk/ Using electricity and small parts such as chips to work. Synonyms: solid-state, circuit-based, digital	using electronic circuits	Electronic devices must be switched off during take-off and landing.
Before a noun: electronic device, electronic payment. Electric means carrying or run by electricity while electronic means built from circuits and chips, so an electric kettle is not an electronic one. Electronics as a field is singular.
virtual realityneutral /ˈvɜrtʃuəl riˈæləti/ Computer images and sounds that make you feel inside another world. Synonyms: VR	computer-generated environment	With virtual reality, students can visit ancient Rome without leaving the classroom.
Uncountable and usually shortened to VR, spoken as two letters. No article in general use: virtual reality is improving fast. You experience something in virtual reality, and the modifier form is a virtual reality headset.
cybersecurityneutral /ˌsaɪbərsɪˈkjʊrəti/ The protection of computers and information against attacks. Synonyms: information security, computer security, data protection	protection of computer systems	Companies are investing millions in cybersecurity to protect their customers' data.
Uncountable and written as one word in American usage. It names both a field and an activity, so firms invest in cybersecurity and hire cybersecurity experts. The cyber prefix also gives cyberattack and cybercrime.
to storeneutral /stɔr/ To keep information or things in a place until they are needed. Synonyms: to keep,to save	keep for later use	All the photos are stored automatically in the cloud, so you never lose them.
Store something in, on or at a place: stored in the cloud, stored on a drive. The uncountable noun is storage, not storing. It implies keeping for the future, so you store data but save a file when you press the button.
developerneutral /dɪˈvɛləpər/ A person whose job is creating software or websites. Synonyms: programmer	person who builds software	The developers fixed the problem a few hours after it was reported.
In technology a developer writes software, while in property a developer builds houses, so context decides which. The verb develop needs an object here: develop an app. Web developer and game developer are common.
to encryptneutral /ɪnˈkrɪpt/ To change information into a secret code so others cannot read it. Synonyms: encode, scramble, put into code	put into secret code	All the messages are encrypted so that nobody else can read them.
You encrypt the message or encrypt a drive, and the passive is very common: the data is encrypted at rest. End-to-end encrypted is a fixed modifier. The noun is encryption and the opposite verb decrypt.
to codeneutral /koʊd/ To write instructions in a language that computers understand. Synonyms: to program	write computer instructions	She learned to code by watching free videos online.
The noun code is uncountable, so a lot of code and never many codes. As a verb it usually stands alone when it names the activity: she can code, learn to code. With an object it means write the program for something: code a website.
programmerneutral /ˈproʊˌɡræmər/ A person who writes computer programs. Synonyms: developer,coder	person who writes programs	The programmers worked all night to get the system working again.
Spelled with a double m in American English even though program itself has one. A programmer writes code, while a developer usually covers a wider job including design and testing. The activity is programming.
bugneutral /bʌɡ/ A mistake in a computer program that stops it working correctly. Synonyms: fault,error	fault in a program	The update fixed a serious bug that made the app close suddenly.
Bugs are found, reported, fixed and introduced, and a bug in the code is the usual pattern. The verb debug means remove them. Other senses: an insect, a hidden listening device, and informally an illness.
serverneutral /ˈsɜrvər/ A powerful computer that stores information and sends it to other computers. Synonyms: host, host machine, host computer	computer that serves others	The website went down because too many people connected to the server at once.
Servers go down, crash and come back up, and they are hosted somewhere. You connect to a server and store files on it. The matching term is client, the machine that asks for the data.
to installneutral /ɪnˈstɔl/ To put a program onto a computer so that it can be used. Synonyms: set up, load, put in place	set up for use	You should install the latest version before the old one stops working.
Install something on a device: installed on my laptop. The noun is installation, while an install as a noun is technical jargon. Uninstall is the opposite. It also covers equipment: install a boiler, install a camera.
operating systemneutral /ˈɑpəˌreɪtɪŋ ˈsɪstəm/ The main program that controls how a computer or phone works. Synonyms: OS, system software, platform	main controlling program	The phone still works, but its operating system is no longer updated.
You run or update an operating system, and a program runs on one. Commonly shortened to OS, spoken as two letters. Windows, macOS, Android and Linux are the usual examples.
cloud computingneutral /ˈklaʊd kəmˈpjutɪŋ/ Storing and using programs and files on the internet instead of your computer. Synonyms: internet-based computing, hosted computing, remote computing	computing over the internet	Thanks to cloud computing, you can open your files from any computer in the world.
The short form is the cloud, always with the: stored in the cloud, moved to the cloud. The full phrase takes no article and no plural. As a modifier it gives cloud storage and cloud services.
user-friendlyneutral /ˌjuzər ˈfrɛndli/ Easy to use, even for people without technical knowledge. Synonyms: simple,easy	easy to use	The new interface is much more user-friendly than the previous one.
Hyphenated in both positions: a user-friendly design, the app is user-friendly. Use more and most for comparison rather than an er ending. The friendly pattern is productive: eco-friendly, budget-friendly, beginner-friendly.
to hackneutral /hæk/ To enter a computer system without permission, often to steal information. Synonyms: break in, breach, compromise	break into a system	The bank's system was hacked, and thousands of passwords were stolen.
Hack into a system, or hack a system directly; both patterns are used, and the passive is very common: we were hacked. A hacker is not always criminal, hence the phrase ethical hacker. Informally a hack is a clever shortcut.
computer scienceneutral /kəmˈpjutər ˈsaɪəns/ The study of computers and how to program them. Synonyms: computing, informatics, CS	the study of computing	She is studying computer science because she wants to work in artificial intelligence.
Uncountable and used with no article: she studies computer science, a degree in computer science. It takes a singular verb: computer science is competitive. American students often shorten it to CS in speech.
to crash (computer)neutral /kræʃ/ To suddenly stop working, used about computers and programs. Synonyms: fail, go down, stop working	stop working suddenly	My computer crashed and I lost the document I had been writing all morning.
Normally with no object: the program crashed. It can also take one: the update crashed my laptop. The noun is a crash. The same verb covers vehicles and markets, as in the market crashed in 2008.
to transmitformal /trænzˈmɪt/ To send out signals, sounds, or information from one place to another. Synonyms: to send,to broadcast	send out; pass on	The signal is transmitted from the satellite to receivers on the ground.
Double the t before an ending: transmitted, transmitting. Transmit something to a receiver, or from one point to another. It is also the standard verb for diseases passed between people. The noun is transmission.
to generateneutral /ˈdʒɛnəˌreɪt/ To produce something such as energy, heat, or ideas. Synonyms: to produce,to create	produce; create	The turbines generate enough electricity for half the city.
Takes a direct object: generate electricity, generate income, generate interest. It suits things produced in quantity rather than single objects, so you generate power but build a house. The machine is a generator.
to convertneutral /kənˈvɜrt/ To change something from one form into another. Synonyms: to change,to turn	change into another form	The panels convert sunlight into electricity that can be stored for later.
Convert something into or to something else: convert sunlight into electricity, convert to the metric system. The noun is conversion, while a convert, stressed on the first syllable, is a person who has changed belief.
asteroidneutral /ˈæstəˌrɔɪd/ A large rock that moves around the Sun in space. Synonyms: space rock, minor planet, planetoid	small rocky space body	Scientists are watching an asteroid that will pass close to the Earth next year.
An asteroid is rock, a comet is ice and grows a tail, and a meteor is the streak of light one makes as it burns up. Asteroids orbit the Sun, pass close to Earth and occasionally strike it, and the asteroid belt lies between Mars and Jupiter.
black holeneutral /ˈblæk ˈhoʊl/ An area in space with gravity so strong that even light cannot leave. Synonyms: collapsed star, region light cannot escape	region of extreme gravity	Nothing, not even light, can escape from a black hole.
Two words and countable. Things fall into a black hole and nothing escapes from one. Figuratively it names anywhere resources disappear: the project became a financial black hole.
light yearneutral /ˈlaɪt ˌjɪr/ The distance that light travels in one year. Synonyms: unit of distance, astronomical distance, interstellar distance	distance light covers yearly	The nearest star is more than four light years away from us.
It measures distance, not time, which is the mistake the name invites. Countable: four light years away. Often written light-year with a hyphen, and light-years is used loosely to mean far ahead of something.
electronneutral /ɪˈlɛkˌtrɑn/ An extremely small part of an atom that carries electricity. Synonyms: subatomic particle, charged particle, negative particle	negatively charged atomic particle	Electricity is simply the movement of electrons through a material.
The three particles come as a set: an electron is negative, a proton positive and a neutron neutral. A flow of electrons through a material is an electric current, and the adjective electronic is built from this word.
nuclearneutral /ˈnukliər/ Using the energy that is released when atoms are split. Synonyms: atomic, fission-based, atomic-energy	of atomic energy	Some countries are closing their nuclear power stations for safety reasons.
Nuclear power, nuclear weapons and nuclear waste are the standard pairs. The pronunciation has three syllables in the order nu-cle-ar; the common swapped version is widely criticized. The noun is nucleus, plural nuclei.
velocityformal /vəˈlɑsəti/ The speed of something moving in a particular direction. Synonyms: speed	speed in a direction	The rocket must reach a velocity of about eleven kilometers per second to leave the Earth.
In physics velocity includes direction while speed does not, so two objects at the same speed may have different velocities. Uncountable in general use but countable for a stated figure: a velocity of eleven kilometers per second.
to accelerateneutral /əkˈsɛləˌreɪt/ To move faster, or to make something move faster. Synonyms: to speed up	speed up	The particles are accelerated until they travel at almost the speed of light.
Used with or without an object: the car accelerated, the magnets accelerate the particles. Accelerate to a speed, or accelerate from rest. The noun is acceleration and the opposite verb is decelerate.
microscopeneutral /ˈmaɪkrəˌskoʊp/ An instrument that makes very small things look much bigger. Synonyms: magnifier, magnifying instrument, optical instrument	instrument for magnifying	Under the microscope, a drop of water is full of tiny living things.
You look at a sample through or under a microscope. The fixed phrase under the microscope also means under close examination. The adjective microscopic means far too small for the eye to see.
electric currentneutral /ɪˈlɛktrɪk ˈkɜrənt/ The flow of electricity through a wire or material. Synonyms: current, flow of charge, electrical flow	flow of electricity	An electric current flows through the wire when you press the switch.
Current here means a flow, the same sense it has in a river, so keep it apart from the adjective current, which means present-day. The frame is an electric current flows through the wire.
vaccinationneutral /ˌvæksəˈneɪʃən/ The act of giving people a substance that protects them from a disease. Synonyms: immunization, inoculation, shot	protective immunizing treatment	Thanks to mass vaccination, the disease has almost disappeared in Europe.
It takes against for the disease, and the verb follows the same pattern: vaccinate someone against something. The substance itself is a vaccine. Countable for one event, uncountable for a program: two vaccinations, mass vaccination.
immunityformal /ɪˈmjunəti/ The body's ability to fight a disease and not become ill. Synonyms: resistance, protection, disease resistance	resistance to disease	The vaccine provides immunity that lasts for at least ten years.
Immunity to measles or immunity against a virus: those are the two prepositions. Immunity builds up, wanes or is acquired. A separate legal sense is protection from prosecution, as in diplomatic immunity. The adjective is immune.
pandemicneutral /pænˈdɛmɪk/ A disease that spreads across many countries of the world. Synonyms: global epidemic, global outbreak, worldwide outbreak	worldwide disease outbreak	During the pandemic, millions of people had to work from home.
Three words scale up together: an outbreak is local, an epidemic spreads through one region, and a pandemic crosses many countries. Endemic is different again and means permanently present somewhere. Usually with the: during the pandemic.
organneutral /ˈɔrɡən/ A part of the body, such as the heart, that does a special job. Synonyms: body part, bodily organ, internal part	specialized body part	Thousands of lives are saved every year by people who donate their organs.
Internal organs, vital organs, organ donation and an organ transplant are the frequent combinations, and organ failure is the medical phrase for one stopping work. The same spelling names the musical instrument, so context decides.
hormoneneutral /ˈhɔrˌmoʊn/ A chemical made by the body that controls how it grows and works. Synonyms: chemical messenger, body chemical, signaling chemical	chemical body messenger	This hormone controls how much energy the body uses during the day.
Hormones are produced, released and regulated by glands, and it is hormone levels that rise or fall rather than the hormone itself. The adjective is hormonal, as in hormonal changes, which moves the stress to the second syllable.
to cloneneutral /kloʊn/ To make an exact copy of a living thing from its cells. Synonyms: copy, replicate, duplicate	make an exact copy	Dolly the sheep was the first mammal to be cloned from an adult cell.
Takes a direct object and is often passive: the sheep was cloned. You clone something from a cell. The noun clone is countable, and in computing to clone means copy a repository or a device exactly.
photosynthesisformal /ˌfoʊtoʊˈsɪnθəsɪs/ The process by which plants make food using light from the Sun. Synonyms: light-driven food making, food production in plants, carbon fixation	plants' food-making process	Through photosynthesis, plants turn sunlight, water and carbon dioxide into food.
Through photosynthesis and during photosynthesis are the usual frames, with no article. Stress falls on the third syllable, the syn. The adjective is photosynthetic, and the verb photosynthesize is used of plants themselves.
oxygenneutral /ˈɑksɪdʒən/ The gas in the air that living things need to breathe. Synonyms: O2, breathable gas, life-supporting gas	the gas we breathe	At high altitude there is less oxygen in the air, so breathing becomes harder.
Oxygen is not the same thing as air, which is mostly nitrogen. Its chemical symbol is O and the gas itself is O2. No article in general statements: oxygen levels, short of oxygen. Related forms: oxide, oxidize.
carbon dioxideneutral /ˌkɑrbən daɪˈɑksaɪd/ The gas produced when we breathe out or when fuel is burned. Synonyms: CO2, carbonic gas, greenhouse gas	the gas CO2	Cars and factories release huge amounts of carbon dioxide into the atmosphere.
Plants absorb it and animals breathe it out, and carbon dioxide traps heat, with no article in such general statements. Often shortened to CO2, spoken as see-oh-two, and dioxide is stressed on its middle syllable.
renewableneutral /rɪˈnuəbəl/ Describing energy that never runs out, such as sun or wind power. Synonyms: sustainable, inexhaustible, replenishable	endlessly replaceable	By 2035, most of the country's electricity will come from renewable sources.
Usually before a noun: renewable energy, renewable sources. The plural noun renewables means renewable power itself. The opposite is non-renewable. A separate everyday sense is able to be extended, as in a renewable contract.
solar panelneutral /ˈsoʊlər ˈpænəl/ A flat piece of equipment that turns sunlight into electricity. Synonyms: photovoltaic panel, PV panel, solar module	sunlight electricity panel	The solar panels on the roof produce more energy than the house needs.
Panels are installed, fitted or mounted on a roof, and they generate or produce electricity, so the plural is the normal form. A large field of them is a solar farm. Solar means of the Sun, as in solar energy.
wind turbineneutral /ˈwɪnd ˈtɜrbaɪn/ A tall machine with blades that uses wind to make electricity. Synonyms: wind generator, turbine, windmill generator	wind-powered generator	Each wind turbine can supply electricity to around a thousand homes.
Turbines are built, installed and switched on, and they turn or spin. The second syllable of turbine is said either like bine or with a reduced bin, and both are standard in American English. A group of them together is a wind farm.
fossil fuelneutral /ˈfɑsəl ˌfjuəl/ A fuel such as coal, oil, or gas formed underground over millions of years. Synonyms: carbon fuel, hydrocarbon fuel, nonrenewable fuel	coal, oil or gas	Burning fossil fuels is the main cause of global warming.
Fossil here means formed from ancient remains, not old-fashioned. They are burned, extracted and phased out, usually in the plural: fossil fuels are burned. Uncountable when it names the category: reliance on fossil fuel.
emissionformal /ɪˈmɪʃən/ Gas or other substances sent into the air, especially harmful ones. Synonyms: discharge, release, output	released gas or substance	The new law requires companies to cut their emissions by half before 2030.
Cut emissions, carbon emissions, net-zero emissions: the plural is the normal form in environmental writing. Uncountable when it means the act of giving out, as in the emission of light. The verb is emit, doubling the t before endings.
greenhouse gasneutral /ˈɡrinˌhaʊs ˌɡæs/ A gas that traps heat in the atmosphere and warms the planet. Synonyms: heat-trapping gas, warming gas, climate gas	heat-trapping gas	Methane is a greenhouse gas far more powerful than carbon dioxide.
Greenhouse compares the atmosphere to glass that holds heat in, which is also why the warming itself is called the greenhouse effect. Usually plural, and shortened to GHG in technical writing.
global warmingneutral /ˈɡloʊbəl ˈwɔrmɪŋ/ The slow rise in the Earth's temperature caused by human activity. Synonyms: planetary warming, rising temperatures, heating of the planet	rising planetary temperature	If global warming continues at this rate, sea levels will rise dangerously.
It names the temperature rise itself, while climate change covers the wider set of effects, so careful writing does not treat them as the same thing. No article and no plural: global warming continues.
climate changeneutral /ˈklaɪmət ˌtʃeɪndʒ/ Long-term changes in the world's weather caused mainly by human activity. Synonyms: climate crisis, changing climate, climate disruption	long-term climate shift	Climate change is already affecting how and where food is grown.
Common with tackle, combat, address and mitigate. It is broader than global warming because it also covers rainfall, storms and sea level. No article and a singular verb: climate change is accelerating.
carbon footprintneutral /ˈkɑrbən ˈfʊtˌprɪnt/ The amount of carbon dioxide that your activities produce. Synonyms: emissions total, carbon impact, climate impact	total emissions caused	Flying less is one of the easiest ways to reduce your carbon footprint.
Countable and usually with a possessive: your carbon footprint, the company's carbon footprint. You reduce, cut, lower or offset one. Footprint here means the mark your activity leaves behind, not an actual print.
recyclingneutral /riˈsaɪklɪŋ/ Treating used objects so that the materials can be used again. Synonyms: reprocessing, reuse, material recovery	reusing waste materials	Recycling saves energy as well as reducing the amount of rubbish we produce.
Uncountable, so no a recycling. The verb is recycle and the adjective recyclable, which describes what can be recycled rather than what has been. Recycling also names the collected material: put it in the recycling.
power stationneutral /ˈpaʊər ˌsteɪʃən/ A large building where electricity is produced. Synonyms: power plant, generating station, electricity plant	electricity generating plant	The old coal power station is being replaced by a solar farm.
It is named by its fuel: a coal power station, a nuclear power station. Stations are built, run and shut down. Power station is the usual British form, while Americans more often say power plant.
electric vehicleneutral /ɪˈlɛktrɪk ˈviɪkəl/ A car or other vehicle that runs on electricity instead of petrol. Synonyms: EV, electric car, battery-powered vehicle	battery-powered car	Electric vehicles are becoming cheaper as batteries improve.
Countable and very often shortened to EV, spoken as two letters. Use electric here rather than electrical, and remember that American English says gas where British English says petrol for the fuel it replaces.
energy-efficientneutral /ˌɛnərdʒi ɪˈfɪʃənt/ Using little energy to do its job, without wasting any. Synonyms: low-energy, efficient, economical	using little energy	Replacing old windows makes a house far more energy-efficient.
Hyphenated before a noun and usually after the verb too: an energy-efficient home, the design is energy-efficient. Compare it with more and most. The matching noun phrase is energy efficiency, written without a hyphen.
deforestationformal /ˌdiˌfɔrɪˈsteɪʃən/ The cutting down of forests over a large area. Synonyms: forest clearance, forest loss, tree felling	large-scale forest clearance	Deforestation destroys the habitats of thousands of species every year.
Uncountable, so no a deforestation and no plural. It is caused, driven, halted or reduced. The opposite processes have their own words: reforestation replants cleared land and afforestation plants where no forest stood.
conservationneutral /ˌkɑnsərˈveɪʃən/ The protection of nature, animals, and important places. Synonyms: protection, preservation, stewardship	protection of nature	Money from visitors pays for the conservation of the national park.
Preservation keeps something unchanged while conservation manages and maintains it. It takes of for what is looked after: the conservation of the park. The person is a conservationist, and in physics conservation of energy is a separate technical sense.
sustainableneutral /səˈsteɪnəbəl/ Able to continue for a long time without damaging the environment. Synonyms: green, eco-friendly	able to continue indefinitely	We need to find more sustainable ways of producing food for a growing population.
Usually before a noun: sustainable farming, sustainable growth. It means able to carry on without using up what it depends on, so something cheap is not automatically sustainable. The noun is sustainability and the verb sustain.
pollutantformal /pəˈlutənt/ A substance that makes air, water, or soil dirty and dangerous. Synonyms: contaminant, toxin, harmful substance	harmful polluting substance	The factory was fined for releasing dangerous pollutants into the river.
A pollutant is the substance itself, while pollution is the dirty condition it creates; pollution is uncountable but pollutants are counted. Usually plural: pollutants are released or discharged into air, water or soil. The verb is pollute.
hydrogenneutral /ˈhaɪdrədʒən/ The lightest gas, used as a clean fuel and found in water. Synonyms: H2, hydrogen gas, the lightest gas	the lightest element	Some buses in the city already run on hydrogen instead of diesel.
Green hydrogen and hydrogen fuel cell are the common modern combinations. Its symbol is H and the gas is H2. No article in general statements: hydrogen burns cleanly.
materialneutral /məˈtɪriəl/ A substance that things are made from, such as metal or plastic. Synonyms: substance	substance; stuff	Scientists are testing a new material that repairs itself when it breaks.
Countable when you mean a type: three different materials. Uncountable for quantity: not enough material. Raw materials is fixed and always plural. As an adjective it means physical, as in material damage.
steelneutral /stil/ A strong metal made from iron, used in buildings and machines. Synonyms: carbon steel, alloy, metal	strong iron-based metal	The bridge is made of steel that can resist extremely strong winds.
It sounds identical to steal, the verb meaning take without permission. Stainless steel and steel beam are common, and the noun is uncountable: made of steel, a ton of steel. Steel yourself means prepare for something difficult.
plasticneutral /ˈplæstɪk/ A light artificial material that can be made into many shapes. Synonyms: polymer, synthetic material, resin	artificial moldable material	Millions of tonnes of plastic end up in the ocean every year.
Single-use plastics shows the countable use for types, while the substance itself is uncountable. As an adjective it normally means made of plastic, but in technical use plastic also means able to be shaped, which gives the noun plasticity.
structureneutral /ˈstrʌktʃər/ The way that the parts of something are built or organized. Synonyms: framework, arrangement, construction	arrangement of parts	The structure of the building was designed to survive strong earthquakes.
Countable when it means a built thing or a pattern, uncountable when it means organization in general: the plan lacks structure. The verb structure means organize, and the adjective structural refers to the load-bearing parts.
infrastructureformal /ˈɪnfrəˌstrʌktʃər/ The basic systems that a country needs, such as roads and power. Synonyms: basic facilities, public works, basic systems	basic public systems	The country needs to invest heavily in infrastructure such as roads and railways.
Uncountable, so no an infrastructure and no plural in careful writing. You invest in, build, upgrade or maintain infrastructure. It covers roads, power, water and networks together, so it is far broader than one structure.
mechanismneutral /ˈmɛkəˌnɪzəm/ A set of moving parts that work together in a machine. Synonyms: workings, machinery, moving parts	system of moving parts	The clock still works thanks to a mechanism built more than two centuries ago.
Beyond moving parts it names any process that makes something happen: a mechanism for settling disputes, the mechanism of infection. It takes for plus a purpose and of plus what it explains. The adjective mechanical belongs only to machines.
componentformal /kəmˈpoʊnənt/ One of the parts that a machine or system is made of. Synonyms: part,piece	part of a whole	Each component is tested separately before the machine is put together.
A part is any piece, while a component is a piece of a designed system, which is why factories order components and not parts. It takes of: a component of the engine. It also works as an adjective, as in the component parts.
engineneutral /ˈɛndʒən/ The part of a vehicle or machine that produces movement. Synonyms: motor	motor; power unit	The engine converts the energy in the fuel into movement.
An engine traditionally burns fuel while a motor runs on electricity, though the two words overlap in everyday speech. Engines start, run, stall and are switched off. Search engine borrows the word for software.
durableneutral /ˈdʊrəbəl/ Staying in good condition for a long time, even with much use. Synonyms: strong,tough	long-lasting; hard-wearing	The phone case is made from a durable material that absorbs shocks.
It describes physical toughness rather than length of time alone, so a durable case survives being dropped. The noun is durability, and consumer durables means goods meant to last for years.
transparentneutral /trænsˈpɛrənt/ Clear enough to see through, like glass. Synonyms: clear	see-through; clear	The scientists created a material almost as transparent as glass but much stronger.
Translucent lets light through without a clear image, while transparent lets you see the object behind it. Figuratively it means open and honest: a transparent process. The noun is transparency.
syntheticneutral /sɪnˈθɛtɪk/ Made by people from chemicals, not natural. Synonyms: artificial,man-made	made from chemicals	Synthetic materials are often cheaper, but natural ones feel better.
Usually before a noun: synthetic fiber, synthetic rubber. Its opposite here is natural. It is neutral in technical writing but can sound negative about food or fabric. The verb is synthesize and the noun synthesis.
nanotechnologyformal /ˌnænoʊtɛkˈnɑlədʒi/ Science that works with extremely small things, at the size of atoms. Synonyms: nanoscale engineering, nanoscience, nanotech	engineering at atomic scale	Nanotechnology works with materials thousands of times smaller than a human hair.
Uncountable and often shortened to nanotech, and it takes a singular verb: nanotechnology is advancing. The nano prefix means one billionth, which also gives nanometer and nanosecond. The adjective is nanoscale.
measurementneutral /ˈmɛʒərmənt/ The size or amount of something found by measuring it. Synonyms: reading, figure, recorded value	recorded size or amount	The measurements were repeated three times to make sure they were accurate.
Countable for a single figure and usually plural for a set: take the measurements. Uncountable when it means the activity: units of measurement. You take, record or repeat a measurement. The verb is measure.
to measureneutral /ˈmɛʒər/ To find the exact size, amount, or level of something. Synonyms: gauge, quantify, determine	find the exact amount	The instrument measures changes in temperature as small as one thousandth of a degree.
It can link two things with no object at all: the room measures four meters. Otherwise it takes an object, as in measure the length, and measure in plus a unit gives measured in degrees. The result is a measurement.
accurateneutral /ˈækjərət/ Correct and exact, without mistakes. Synonyms: exact,correct	correct; free of error	The forecast is surprisingly accurate up to five days in advance.
Accurate means close to the true value while precise means finely detailed and repeatable, so a figure can be precise and still be wrong. Stress is on the first syllable. The noun is accuracy and the adverb accurately.
preciseneutral /prɪˈsaɪs/ Exact and clear, with all the small details correct. Synonyms: exact, specific	exact; finely detailed	The operation requires precise movements that only a robot can repeat perfectly.
Precise says how finely something is specified, accurate whether it is right: a scale that always reads two kilos heavy is precise but not accurate. The noun is precision, and to be precise is a fixed phrase for adding an exact figure.
to calculateneutral /ˈkælkjəˌleɪt/ To find an answer or amount by using mathematics. Synonyms: to work out	work out using math	The computer can calculate in seconds what would take a person years.
Takes an object or a clause: calculate the cost, calculate how long it will take. The noun is calculation and the machine a calculator. Calculate suits arithmetic, while work out is the everyday equivalent.
proportionneutral /prəˈpɔrʃən/ A part or share of a total amount. Synonyms: share,part	share of a total	A large proportion of the energy we use is still wasted.
The verb follows the noun after of, so a proportion of the energy is wasted but a proportion of the houses were destroyed. In proportion to and out of all proportion are fixed. The adjective is proportional.
dimensionneutral /dəˈmɛnʃən/ A measurement of something in length, width, or height. Synonyms: measurement, extent, size	measurement of extent	Write down the dimensions of the room before you order the furniture.
Usually plural for the size of an object: the dimensions of the room. Singular for an aspect of something: a political dimension. In physics three dimensions means length, width and height together.
depthneutral /dɛpθ/ The distance from the top of something down to the bottom. Synonyms: deepness, vertical distance, drop	distance downward	The robot can work at a depth of four thousand meters under the sea.
Uncountable for the quality and countable for a stated figure: at a depth of four thousand meters. In depth means thoroughly, and out of your depth means beyond your ability. The matching adjective is deep.
scaleneutral /skeɪl/ The size or level of something, especially when it is large. Synonyms: extent, magnitude, size	size; level of extent	The damage caused by the storm was on a scale nobody had predicted.
Uncountable in on a large scale and on this scale. Countable for a graded series: the Richter scale, a scale of one to ten. Scale up and scale down mean grow or shrink deliberately. Scales for weighing is a separate sense.
on averageneutral /ɑn ˈævərɪdʒ/ Used to describe what is usual or typical when numbers are compared. Synonyms: typically, generally, as a rule	typically; as a mean	On average, the new batteries last twice as long as the old ones.
In average is an error: the preposition is on. It usually opens a clause with a comma after it, or sits after the verb, and takes no article. The related noun phrase is the average of, and the verb is average out.
chemical reactionneutral /ˈkɛmɪkəl riˈækʃən/ A process in which substances change and become different substances. Synonyms: chemical change, chemical process, reaction	chemical change process	The chemical reaction produces heat, which is used to warm the building.
Countable: a chemical reaction takes place or occurs. Substances react with each other to form something new, so a reaction is more than mixing. Reactions can be fast, violent, reversible or heat-producing.
to dissolveneutral /dɪˈzɑlv/ To mix completely with a liquid and seem to disappear. Synonyms: break down, go into solution, melt away	mix into a liquid	Sugar dissolves much faster in hot water than in cold.
Dissolve in a liquid, not into it: sugar dissolves in water. It works with or without an object, so heat dissolves the salt and the salt dissolves. The noun is solution and the adjective soluble. A formal sense is to end a partnership.
to evaporateneutral /ɪˈvæpəˌreɪt/ To change from a liquid into a gas, especially when heated. Synonyms: vaporize, turn to gas, dry up	turn into vapor	When water evaporates, the salt is left behind at the bottom of the container.
Normally used with no object: the water evaporated. The noun is evaporation and the reverse process is condensation. Figuratively it means disappear quickly, as in their support evaporated overnight.
to absorbneutral /əbˈzɔrb/ To take in liquid, heat, or energy little by little. Synonyms: to take in	soak up; take in	Dark surfaces absorb more heat than light ones, which is why they feel hotter.
Takes a direct object: absorb heat, absorb water, absorb a shock. The noun is absorption, which swaps the b of absorb for a p. Absorbed in something means deeply concentrated on it.
to detectneutral /dɪˈtɛkt/ To notice or find something that is not easy to see. Synonyms: to find,to notice	notice; find traces of	The test can detect the disease years before the first symptoms appear.
Takes a direct object: detect a leak, detect a change. Often passive, as in no radiation was detected. The noun is detection, the device a detector, and detectable means possible to find.
to inventneutral /ɪnˈvɛnt/ To create or design something that did not exist before. Synonyms: to create	create something new	The telephone was invented about one hundred and fifty years ago.
You invent what did not exist and discover what already did. Often passive with by: invented by Bell. The noun is invention and the person an inventor. Invent also means make up something untrue: invent an excuse.
to modifyformal /ˈmɑdəˌfaɪ/ To change something slightly to improve it. Synonyms: to change,to adapt	change slightly	The design was modified several times before the final version was approved.
Takes a direct object: modify the design. The change is partial, so a modified version is still recognizable while a transformed one is not. The noun is modification. In grammar, a word that modifies another describes it.
to transformneutral /trænsˈfɔrm/ To change something completely, usually making it better. Synonyms: to change	change completely	The internet has completely transformed the way we communicate with each other.
Transform something into something else, or be transformed by an event. The change is total, which is what separates it from modify or adjust. The noun is transformation and the device a transformer.
to operateneutral /ˈɑpəˌreɪt/ To work or function, or to control a machine. Synonyms: to work,to function	run; control a machine	The machine can operate for twenty-four hours without any human control.
In medicine you operate on a patient, never operate a patient. With no object it means work, as in the plant operates around the clock; with an object it means control, as in operate a crane. The noun is operation.
objective (adjective)formal /əbˈdʒɛktɪv/ Based only on facts, not influenced by personal feelings. Synonyms: impartial, neutral, even-handed	fact-based; unbiased	Scientists must remain objective and ignore their personal opinions.
Its opposite is subjective, meaning shaped by personal feeling. The noun objectivity is uncountable. An identical noun, objective, means a goal, so an objective report and your main objective use different words with one spelling.
sophisticatedneutral /səˈfɪstəˌkeɪtɪd/ Advanced and complicated in the way it works. Synonyms: advanced,complex	advanced; highly developed	Modern weather models are sophisticated enough to predict storms a week ahead.
Of machines and methods it means complex and capable, and it is a compliment. Of people it means worldly and cultured. Stress falls on the second syllable, and the noun is sophistication.
state-of-the-artneutral /ˌsteɪt əv ði ˈɑrt/ Using the newest and most advanced methods or technology. Synonyms: advanced,modern	most advanced available	The hospital has just opened a state-of-the-art operating theater.
Hyphenated before a noun: state-of-the-art equipment. After a verb the hyphens are usually dropped: the lab is state of the art. It is always approving and has no comparative or superlative form.
outdatedneutral /ˌaʊtˈdeɪtɪd/ Old and no longer useful because better things now exist. Synonyms: old-fashioned	obsolete; superseded	The equipment in the school lab is outdated and needs replacing.
Used before a noun and after a verb alike: outdated software, the rules are outdated. Out of date means the same and takes hyphens only before a noun. It is disapproving, whereas old is simply neutral.
portableneutral /ˈpɔrtəbəl/ Light and easy to carry or move. Synonyms: mobile,light	easily carried	The scanner is light and portable, so nurses can carry it from room to room.
It means designed to be carried, so a portable heater is small by design rather than merely movable. The noun is portability, and in computing portable code runs on many systems.
high-techneutral /ˌhaɪ ˈtɛk/ Using the most modern machines and methods. Synonyms: advanced,modern	using advanced technology	The city has become a center for high-tech companies from all over the world.
Hyphenated in both positions and also written hi-tech: a high-tech firm, the lab is high-tech. The full form is high technology. Its opposite low-tech is often approving, meaning simple and dependable.
peer reviewformal /ˈpɪr rɪˌvju/ The checking of scientific work by other experts before it is published. Synonyms: expert review, expert assessment, refereeing	expert checking before publication	Every serious article goes through peer review before it is published.
Uncountable and usually with no article: subject to peer review, go through peer review. The participle is hyphenated before a noun: a peer-reviewed journal. A peer here means a fellow specialist, not a nobleman.
case studyformal /ˈkeɪs ˌstʌdi/ A detailed study of one person, group, or situation over time. Synonyms: detailed study, case analysis, case report	detailed single-case examination	The book includes a detailed case study of how one hospital reduced infections.
Countable: several case studies. The pattern is a case study of or on something. Because it examines one case closely, it cannot show what is typical of a whole population, which is what a survey does.
in practiceneutral /ɪn ˈpræktɪs/ Used to say what really happens rather than what should happen. Synonyms: in the real world, in actual fact	in reality; actually	The idea sounds simple, but in practice it is difficult to apply.
A fixed phrase with no article, usually marked off by a comma and used to correct an expectation, which is why it so often answers in theory. Note the spelling with c; practise with an s is the British verb form.
cause and effectneutral /ˈkɔz ənd ɪˈfɛkt/ The relationship between something that happens and the thing that makes it happen. Synonyms: causal link, causation, causal relationship	causal relationship	It is hard to prove cause and effect between diet and disease.
A fixed phrase with no articles and no plural, and the order never reverses. Common after show, prove or establish: hard to prove cause and effect. The related adjective is causal, which is not the word casual.
to compressneutral /kəmˈprɛs/ To press something into a smaller space, or make a file smaller. Synonyms: to squeeze	squeeze into less space	The files are compressed before they are sent to the server.
Takes a direct object: compress the gas, compress a file. Double the s before endings: compressed, compression. A compressed file is smaller but complete, not damaged. Compressed air is a fixed phrase.
to filterneutral /ˈfɪltər/ To remove unwanted substances from a liquid, gas, or information. Synonyms: strain, purify, screen	strain out unwanted parts	The water is filtered twice before it reaches our homes.
Filter something, or filter something out: filter out the salt. Filter through means pass slowly, used of news as well as liquid. The noun filter is countable and the process is filtration.
to overheatneutral /ˌoʊvərˈhit/ To become too hot, especially a machine or an engine. Synonyms: get too hot, run too hot, become overheated	become dangerously hot	The laptop shuts down automatically if the battery overheats.
Usually with no object: the engine overheated. It can take one: the fault overheated the battery. The over prefix means excessively, as in overload and overcharge. It is also used of an economy growing too fast.
to malfunctionformal /ˌmælˈfʌŋkʃən/ To stop working correctly, used about machines and systems. Synonyms: to fail	work incorrectly	The probe's cameras malfunctioned shortly after the launch.
Used with no object: the sensor malfunctioned. The same form is a countable noun: a serious malfunction. The mal prefix means badly, as in malnutrition. It is more technical than break down or go wrong.
to degradeformal /dɪˈɡreɪd/ To slowly break down or become worse in quality. Synonyms: break down, decay, deteriorate	break down gradually	Plastic degrades very slowly, so it stays in the ocean for centuries.
With no object it means decay: the plastic degrades slowly. With an object it means make worse: heat degrades the material. The noun is degradation, stressed on the third syllable. A separate sense is to humiliate someone.
to leakneutral /lik/ To let liquid or gas escape through a hole by accident. Synonyms: escape, seep, drip	escape through a hole	If the pipe leaks, the gas detector sets off an alarm.
Both the container and the contents can leak: the pipe leaks, gas leaks out. The noun leak is countable while leakage is the uncountable amount. A separate sense is releasing secret information: leak a document.
to erodeformal /ɪˈroʊd/ To slowly wear away land or material, usually by water or wind. Synonyms: wear away, wear down, eat away	wear away slowly	The coastline is being eroded by rising sea levels.
Used both ways: the cliff is eroding, and the waves erode the cliff. The passive is very common: the coast is being eroded. The noun is erosion. Figuratively it suits any slow loss, as in eroding public trust.
to contaminateformal /kənˈtæməˌneɪt/ To make something dirty or dangerous by adding harmful substances. Synonyms: to pollute	make impure or unsafe	The river was contaminated by chemicals from a nearby factory.
Takes a direct object and is very often passive: the water was contaminated. Contaminated with plus the substance. The noun is contamination and the substance a contaminant. It is stronger than dirty and implies a health risk.
to recycleneutral /riˈsaɪkəl/ To treat used materials so that they can be used again. Synonyms: reprocess, reuse, reclaim	process for reuse	Glass can be recycled again and again without losing quality.
Takes a direct object and is often passive: glass can be recycled. The noun is recycling and the adjective recyclable, which means capable of being recycled rather than already recycled.
to insulateneutral /ˈɪnsəˌleɪt/ To cover something so that heat, sound, or electricity cannot pass through. Synonyms: cover, shield, protect	block heat or current	The cables are insulated with plastic to prevent electric shocks.
Takes a direct object, often with against or from: insulated against the cold. Stress is on the first syllable, and the noun insulation names both the act and the material. It is also used of shielding people from an effect.
to emitformal /ɪˈmɪt/ To send out gas, heat, light, or sound into the air. Synonyms: give off, release, discharge	send out; give off	The engine emits far less carbon dioxide than older models.
Double the t before endings: emitted, emitting. It takes a direct object: emit light, emit carbon dioxide. The noun emission is usually plural in environmental writing, and the device is an emitter.
to upgradeneutral /ˌʌpˈɡreɪd/ To improve a machine or program by adding newer, better parts. Synonyms: to improve	improve to a newer version	The system needs to be upgraded before it can run the new software.
Takes an object and is often passive: the system was upgraded. Upgrade to a newer version. The noun upgrade moves the stress to the first syllable. The opposite is downgrade, used of ratings as well as equipment.
to automateneutral /ˈɔtəˌmeɪt/ To make a machine or computer do a job instead of people. Synonyms: mechanize, computerize, make automatic	make machine-operated	Many factories have automated the tasks that workers used to do by hand.
Takes a direct object: automate the process. The participle automated works as an adjective: an automated reply. The noun is automation, while automatic describes the machine rather than the act of changing it.
to activateneutral /ˈæktəˌveɪt/ To make a machine or system start working. Synonyms: to start,to turn on	switch on; set going	The alarm is activated automatically when the sensor detects smoke.
Takes a direct object and is often passive: the alarm is activated by smoke. The noun is activation and the opposite verb deactivate. It suits systems and devices; people are motivated rather than activated.
toxicneutral /ˈtɑksɪk/ Poisonous and dangerous to people, animals, or the environment. Synonyms: poisonous	poisonous; harmful	The fumes from the fire were highly toxic, so the area was evacuated.
Before a noun: toxic waste, toxic fumes. Toxic to plus what it harms: toxic to fish. The noun is toxicity and a poison itself is a toxin. In recent use it also describes harmful behavior: a toxic workplace.
flammableneutral /ˈflæməbəl/ Able to catch fire easily and burn quickly. Synonyms: combustible, inflammable, burnable	easily set on fire	Hydrogen is highly flammable, so it must be stored with great care.
Flammable and inflammable mean the same thing, which is why safety labels prefer flammable and avoid the confusion. The opposite is non-flammable, and highly flammable is the standard warning phrase.
rechargeableneutral /riˈtʃɑrdʒəbəl/ Able to be filled with electricity and used again. Synonyms: reusable, refillable	able to be recharged	The kit comes with rechargeable batteries that charge in under an hour.
Used of batteries and devices: a rechargeable battery. Keep the e of charge before the able ending. The verb is recharge, which is also used of people resting, as in recharge your batteries.
automaticneutral /ˌɔtəˈmætɪk/ Working by itself without a person controlling it. Synonyms: self-acting, self-operating, mechanical	self-operating	The doors are automatic, so they open as soon as you approach.
Used before a noun and after a verb: an automatic door, the reply is automatic. The adverb automatically is very common. Automatic describes how a thing works, while automated says it was deliberately made that way.
artificialneutral /ˌɑrtəˈfɪʃəl/ Made by people rather than existing naturally. Synonyms: man-made,synthetic	man-made; not natural	The researchers grew artificial skin that heals like real tissue.
Usually before a noun: artificial light, artificial limb. The adverb artificially means by artificial means, as in artificially sweetened. It is neutral in technical use, but of feelings or smiles it means insincere.
experimentalformal /ɪkˌspɛrəˈmɛntəl/ Still being tested and not yet proved to work. Synonyms: untested, unproven, trial	still being tested	The treatment is still experimental and has not been approved for general use.
Of a treatment or design it means not yet approved, so it carries a warning. Of a method it simply means based on experiment: experimental evidence. The adverb experimentally means as a test rather than for real.
self-drivingneutral /ˌsɛlf ˈdraɪvɪŋ/ Able to drive itself without a human driver, using computers. Synonyms: driverless, autonomous, computer-driven	driverless	Self-driving cars must react faster than any human driver.
Hyphenated and normally before a noun: a self-driving car. Autonomous and driverless are the usual alternatives in technical writing. The self prefix is productive: self-cleaning, self-healing, self-locking.
biodegradableneutral /ˌbaɪoʊdɪˈɡreɪdəbəl/ Able to decay naturally without damaging the environment. Synonyms: naturally decaying, breaking down naturally	able to decay naturally	The company has replaced plastic bags with biodegradable ones made from plants.
It means broken down by living organisms, so biodegradable is not the same as recyclable or compostable. The opposite is non-biodegradable, and the stress falls on the fourth syllable, the grad.
resistantneutral /rɪˈzɪstənt/ Not damaged or affected by something. Synonyms: strong,tough	unaffected by something	The new coating makes the metal resistant to rust and extreme heat.
It takes to: resistant to heat, resistant to antibiotics. As the second half of a compound it is hyphenated: heat-resistant, water-resistant. Water-resistant is weaker than waterproof. The noun is resistance.
microscopicneutral /ˌmaɪkrəˈskɑpɪk/ So small that it can only be seen with a microscope. Synonyms: tiny	too small to see	The device removes microscopic particles that ordinary equipment cannot catch.
It means needing a microscope, so microscopic particles are far smaller than merely tiny ones. Stress falls on the third syllable. Figuratively it means extremely detailed: a microscopic examination of the accounts.
interactiveneutral /ˌɪntərˈæktɪv/ Allowing people and computers to communicate and react to each other. Synonyms: hands-on, two-way, user-controlled	two-way; responsive	The museum has interactive screens where visitors can try the experiments themselves.
Usually before a noun: an interactive map, an interactive display. It means the user acts and the system answers, so a video you only watch is not interactive. The noun is interaction and the verb interact with.
remotelyneutral /rɪˈmoʊtli/ From far away, without being physically present. Synonyms: from a distance, at a distance, from afar	from a distance	Engineers can control the robot remotely from the other side of the world.
With work and control it means from another place: work remotely, controlled remotely. After a negative it means in the slightest: not remotely possible. The adjective remote also means far from anywhere.
manuallyneutral /ˈmænjuəli/ Done with the hands rather than by a machine. Synonyms: by hand, physically, without machines	by hand	If the system fails, the doors can be opened manually.
Usually after the verb: opened manually, entered manually. It contrasts directly with automatically. The adjective manual describes work done by hand, while a manual as a noun is an instruction book.
instantlyneutral /ˈɪnstəntli/ Immediately, without any delay. Synonyms: right away, at once	immediately	The results are shared instantly with laboratories all over the world.
Usually before the main verb or at the end of the clause: it loads instantly. Immediately is interchangeable, while instantaneously is longer and more technical. The adjective instant suits nouns: instant access.
in real timeneutral /ɪn ˈriəl ˈtaɪm/ Happening or shown immediately, as events take place. Synonyms: live, as it happens, without delay	as it happens	The app shows you the position of every bus in real time.
A fixed phrase with no article and no hyphens after a verb, but real-time takes a hyphen before a noun: real-time data. It means with no noticeable delay, which is a stronger claim than simply fast.
up to dateneutral /ˌʌp tə ˈdeɪt/ Including the newest information or the most recent improvements. Synonyms: current, recent, modern	current; newest	Keep your software up to date to protect your data from attacks.
Three separate words after a verb but hyphenated before a noun: keep it up to date, up-to-date information. Keep and bring are the usual verbs, as in bring the records up to date. The opposite is out of date.
step by stepneutral /ˌstɛp baɪ ˈstɛp/ Doing one thing after another in a careful order. Synonyms: gradually, systematically, in stages	one stage at a time	The manual explains step by step how to install the equipment.
No hyphens after a verb but hyphenated before a noun: explained step by step, a step-by-step guide. It describes how something is done, so it follows the verb rather than opening the sentence.
on standbyneutral /ɑn ˈstændˌbaɪ/ Ready to be used immediately if needed. Synonyms: ready, in reserve, waiting	ready if needed	The backup generator is always on standby in case the power fails.
A fixed phrase, usually after be, keep or put: kept on standby. Standby is one word as a noun and hyphenated before another noun: a standby generator. Of a device it means drawing little power while switched off.

English B2 — Science & Technology Official

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