Science Vocabulary in English
20 key science vocabulary in english words with meanings, example sentences, and free interactive exercises — ideal for B2–C1 learners.
Science vocabulary sits at the heart of academic English, and mastering it opens doors that general vocabulary alone cannot. Whether you are reading a university textbook, listening to a lecture, watching a documentary, or sitting an IELTS exam, words like hypothesis, variable, and evidence appear constantly. Because these words carry very precise meanings in scientific writing, knowing them accurately — not just approximately — prevents costly misunderstandings in essays, reports, and professional communication.
In everyday life, science language surfaces more often than most learners expect. News articles discuss radiation levels after industrial accidents, climate reports use organism and photosynthesis when explaining ecosystems, and tech podcasts regularly mention energy, velocity, and compound materials. When you encounter these words without solid definitions, you fill the gaps with guesswork, which distorts your understanding of the entire text. Building a reliable bank of science terms transforms passive exposure into active comprehension.
The most effective strategy for learning science vocabulary is to study each word in a real sentence rather than in isolation. Notice how experiment is always conducted, how a hypothesis is formed or tested, and how gravity attracts or pulls. These collocations — the words that travel together — are what make your English sound natural and precise. Use the word list below alongside LexFizz's interactive exercises to move from recognition to active use as quickly as possible.
What You'll Learn
- 20 key science words with clear definitions and natural example sentences at B2–C1 level
- How scientific terms function across disciplines: biology, chemistry, physics, and earth science
- The collocations and grammar patterns that make each word sound accurate in written and spoken English
- How to recognise and use these words confidently in IELTS Academic tasks, university assignments, and science-related reading
Word List
| Word | Meaning | Example Sentence |
|---|---|---|
| hypothesis | a proposed explanation made before it has been fully tested | The scientist formed a hypothesis about cell behaviour. |
| experiment | a scientific test done to discover or prove something | The experiment was conducted under controlled conditions. |
| observation | the action of carefully watching something | Careful observation led to an important discovery. |
| evidence | facts or information indicating whether something is true | The evidence strongly supports the theory. |
| variable | a factor that may change during an experiment | The temperature was the key variable in the experiment. |
| molecule | the smallest unit of a substance that has all the properties of that substance | A water molecule consists of two hydrogen atoms and one oxygen atom. |
| atom | the smallest particle of a chemical element | All matter is made of atoms. |
| element | a substance consisting entirely of atoms of the same type | Oxygen is an element found in air and water. |
| compound | a substance formed from two or more elements chemically joined | Water is a compound of hydrogen and oxygen. |
| reaction | a process in which substances change into new substances | A chemical reaction occurred when the two liquids were mixed. |
| gravity | the force that attracts objects towards the centre of the Earth | Gravity keeps us on the ground. |
| energy | the ability to do work; power derived from physical or chemical resources | Renewable energy comes from sources like the sun and wind. |
| velocity | the speed of something in a given direction | The velocity of the falling object increased rapidly. |
| evolution | the gradual development of species over many generations | Darwin's theory of evolution changed our view of life. |
| cell | the smallest structural unit of a living organism | The human body is made of trillions of cells. |
| gene | a unit of DNA that determines characteristics of a living thing | Genes carry information passed from parents to children. |
| organism | a living thing, such as an animal, plant, or bacterium | Even the smallest organism has complex systems. |
| photosynthesis | the process by which plants make food from sunlight and CO₂ | Photosynthesis produces oxygen as a by-product. |
| radiation | energy emitted as waves or particles, such as light or X-rays | Excessive radiation exposure can damage cells. |
| orbit | the curved path of one object around another in space | The Moon's gravity causes the ocean tides on Earth. |
Practice with These Exercises
Flash Cards
Review words with spaced repetition
Quiz
Test your vocabulary knowledge
Match Up
Match words to their meanings
Wordsearch
Find hidden vocabulary words
Practice What You've Learned
LexFizz has 30 free interactive exercises — no sign-up needed.
Browse All Exercises →Related Vocabulary Topics
Frequently Asked Questions
Why is science vocabulary important for IELTS candidates?
IELTS Academic reading and writing tasks regularly draw on texts from biology, chemistry, physics, and environmental science. Knowing words like hypothesis, variable, and evidence allows you to understand source texts more accurately and write Task 1 and Task 2 responses that sound appropriately academic. Without this vocabulary, even a strong grasp of grammar can leave your writing vague or imprecise.
What is the difference between a hypothesis and a theory in English?
In scientific English, a hypothesis is a testable prediction made before an experiment is carried out, while a theory is a well-supported explanation backed by substantial evidence collected over time. Mixing the two is a common error in learner writing. In everyday English, "theory" is often used loosely to mean a guess, but in academic contexts this usage is considered imprecise.
How do I remember the difference between an atom, a molecule, and a compound?
Think of it as a hierarchy: an atom is the smallest particle of a single element; a molecule is two or more atoms bonded together (they can be the same element, like O₂, or different ones); and a compound is specifically a molecule made of two or more different elements. Visualising the scale — atom inside molecule inside compound — makes the distinction stick quickly.
Is the word "cell" used differently in science and everyday English?
Yes. In everyday English, cell most commonly refers to a prison cell or a mobile phone cell. In biology, it means the smallest structural and functional unit of a living organism. When reading scientific texts, always check the context: if the surrounding words include membrane, nucleus, or divide, the biological meaning applies.
What collocations should I learn for the word "experiment"?
The most common collocations are: conduct an experiment, carry out an experiment, run an experiment, and design an experiment. You would rarely say "make an experiment" in academic English, even though learners from several language backgrounds translate it that way. Practising these fixed phrases alongside the word itself is far more effective than studying definitions alone.
How is "velocity" different from "speed" in scientific English?
Both words describe how fast something moves, but velocity includes a direction, making it a vector quantity, while speed is a scalar with no direction. In physics writing this distinction is critical: a car travelling at 60 km/h has a speed, but travelling at 60 km/h due north has a velocity. In casual English, the two words are often treated as synonyms, but academic science writing requires precision.
Can "radiation" have a positive meaning in English?
Yes. Although radiation is often associated with nuclear hazards, the word simply describes energy emitted as waves or particles. Sunlight is a form of radiation, and medical X-rays, microwave ovens, and MRI machines all involve radiation used beneficially. IELTS and academic texts often discuss radiation in neutral or positive contexts, so treating it as purely negative can lead to misreading a passage.
Why do science words like "photosynthesis" look so long and hard to remember?
Many long science words are built from Greek and Latin roots, which makes them easier to decode once you spot the pattern. Photo- means light, and synthesis means putting together — so photosynthesis literally means "putting together using light." Learning a handful of common roots (bio-, thermo-, geo-, micro-) can help you unlock dozens of science words without memorising each one from scratch.
How should I study science vocabulary if I am not a science student?
Focus on the words that appear most frequently in general academic writing rather than highly specialised technical terms. Words like evidence, observation, evolution, and energy appear across subjects including economics, history, and social studies. Using flash cards, gap-fill exercises, and reading short science news articles are all effective strategies that do not require a scientific background.
Are science vocabulary words useful for everyday English conversation?
More than most learners expect. Words like energy, reaction, element, and gravity are used daily in conversation, often metaphorically: "She brought great energy to the meeting," or "His reaction was unexpected." Understanding both the precise scientific meaning and the metaphorical usage gives you a richer command of the language and helps you sound natural in a wider range of situations.