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Science vocabulary words for students

This list collects essential science vocabulary spanning biology, chemistry, physics, and earth science, from atom and cell to ecosystem and evolution. It suits middle school students building a foundation for lab reports, textbook reading, and classroom discussion, offering a starting set of terms to review before a new unit or quiz.

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Science vocabulary words for students

Word	Meaning	In a sentence
atomnoun	The smallest unit of an element that keeps that element's chemical identity.	A water molecule contains two hydrogen atoms and one oxygen atom.
moleculenoun	The smallest unit of a substance that still has all its chemical properties, made of two or more bonded atoms.	A water molecule consists of two hydrogen atoms bonded to one oxygen atom.
cellnoun	The basic structural and functional unit of living organisms.	We examined an onion cell under the microscope.
organismnoun	An individual living thing.	A single bacterium is an organism.
ecosystemnoun	The living things in an area together with their nonliving surroundings and the ways they interact.	The pond ecosystem includes insects, plants, water, and sediment.
photosynthesisnoun	The process in which plants, algae, and some bacteria use light energy to make sugars.	The leaves use light for photosynthesis.
gravitynoun	The attraction between objects that have mass.	Gravity pulls the falling apple toward Earth.
energynoun	The capacity to do work or bring about change.	Sunlight provides energy that the plant uses to make sugars.
matternoun	Anything that has mass and takes up space.	Air is matter even though we cannot usually see it.
elementnoun	A basic, essential part of something, or a pure chemical substance made of one type of atom.	Trust is a crucial element of any successful long-term relationship.
compoundnoun	A substance formed when two or more chemical elements are combined in fixed proportions.	Water is a compound made of two hydrogen atoms bonded to one oxygen atom.
reactionnoun	A response to something that has happened, been said, or been experienced.	Her immediate reaction to the news was a mixture of shock and relief.
hypothesisnoun	A proposed explanation that can be tested using observations or an investigation.	Our hypothesis was that the seedlings would grow taller with more light.
experimentnoun	A planned test used to investigate a question or test an explanation.	Our experiment compared how quickly sugar dissolved in warm and cool water.
observationnoun	The act of carefully watching or noticing something, or a comment based on what has been noticed.	Careful observation of the birds' behavior revealed a pattern the researchers had missed.
evolutionnoun	The gradual process by which species of organisms change over successive generations.	Darwin's theory of evolution explains how species adapt to their environments over time.
habitatnoun	The place and conditions in which an organism normally lives.	The hedgerow provides habitat for nesting birds.
adaptationnoun	The process of changing to become better suited to new conditions, or a modified version of an original work.	The lizard's coloring is an adaptation that helps it hide from predators.
speciesnoun	A group of living organisms that share common characteristics and can interbreed to produce fertile offspring.	Scientists discovered a new species of frog deep in the rainforest.
mineralnoun	A naturally occurring solid substance with a specific chemical composition, found in rocks and soil.	Quartz is a common mineral found in many types of rock.
magnetismnoun	The physical force that attracts certain materials, such as iron, and repels others; also a person's compelling charm.	The magnetism of the coil was strong enough to lift small metal pins.
frictionnoun	The resistance one surface or object encounters when moving against another, or tension between people.	Friction between the tires and the wet road made the car harder to control.
velocitynoun	The speed of something in a specific direction; the rate at which it moves.	The rocket reached an incredible velocity just seconds after launch.
forcenoun	A push or pull that can change an object's motion or shape.	The force from her hand set the toy car moving.
massnoun	The quantity of matter in an object, measured by its resistance to acceleration; also a large body or quantity of something.	Scientists measured the mass of the asteroid using its gravitational pull.
densitynoun	The mass of a substance per unit of its volume, or, more generally, how tightly packed something is.	Lead has a much higher density than aluminum, so it feels far heavier for its size.
solutionnoun	A uniform mixture in which one or more substances are dissolved in another.	Stirring the salt into water produced a clear solution.
evaporationnoun	The change of a liquid into gas at the liquid's surface.	Evaporation made the shallow puddle smaller during the afternoon.
condensationnoun	The change of a gas into a liquid.	Condensation formed droplets on the cold window.
nucleusnoun	The central part of an atom or cell that contains most of its mass or genetic material.	The cell's nucleus holds the DNA that directs its growth and function.

Science vocabulary by topic

Some words on this list describe living systems, including cell, organism, ecosystem, habitat, adaptation, and species. Others belong to chemistry and physics, such as atom, molecule, element, compound, force, gravity, and velocity. A third group covers the scientific process itself, including hypothesis, experiment, and observation. Grouping the words this way can make them easier to study and apply across different science units.

Frequently asked questions

What kind of vocabulary is considered science vocabulary?

Science vocabulary includes terms for matter and energy, living systems, and the steps of scientific investigation, such as atom, ecosystem, and hypothesis.