A to Z List of Science Words in English | Every Term You Need to Know

Learn common science words with this A-to-Z list of science vocabulary in English. These terms cover many areas of science, from biology and chemistry to physics and space. Understanding these words can help students build confidence when learning or talking about science topics.

Below, you’ll find an A to Z list of science words in English, each with a simple definition. Whether you’re teaching or learning science vocabulary, we’ve got you covered!

A to Z List of Science Words

Science Words That Start with A

• Atom – The smallest unit of matter that makes up everything around us.
• Acid – A substance that tastes sour and can turn blue litmus paper red.
• Adaptation – A change in an organism that helps it survive in its environment.
• Air – The invisible gas that surrounds Earth and contains oxygen.
• Alloy – A mixture of two or more metals.
• Amplitude – The height of a wave from its middle point to the top.
• Amphibian – A cold-blooded animal that lives both in water and on land, like frogs.
• Anaerobic – A process or organism that does not need oxygen to live or work.
• Anatomy – The study of body parts and how they are structured.
• Antibiotic – A medicine that kills bacteria or stops them from growing.
• Antibody – A protein made by the body to fight germs and infections.
• Antigen – A substance that causes the immune system to respond.
• Aquatic – Living or growing in water.
• Archimedes’ Principle – A rule that explains how things float in water.
• Area – The size of a surface, measured in square units.
• Arthropod – An animal with jointed legs and a hard outer shell, like insects and crabs.
• Asexual Reproduction – When an organism makes a copy of itself without needing a mate.
• Astronomy – The study of space, stars, and planets.
• Atmosphere – The layer of gases that surrounds Earth.
• Atomizer – A tool that sprays a fine mist, often used in science experiments.
• Avalanche – A large mass of snow or rocks that suddenly falls down a mountain.
• Axis – An imaginary line around which something spins, like Earth.

Science Words That Start with B

• Bacteria – Tiny living things that can be helpful or cause illness.
• Balance – A tool used to measure the mass of an object.
• Barometer – An instrument used to measure air pressure.
• Base – A substance that feels slippery, tastes bitter, and turns red litmus paper blue.
• Battery – A device that stores and provides electrical energy.
• Behavior – The way an organism acts or responds to its environment.
• Biodiversity – The variety of different living things in an area.
• Biology – The study of living things.
• Biome – A large natural area with specific plants, animals, and climate.
• Biosphere – The part of Earth where life exists.
• Boiling Point – The temperature at which a liquid turns into a gas.
• Botany – The study of plants.
• Brain – The organ that controls the body and helps us think and feel.
• Breathing – The process of taking in oxygen and releasing carbon dioxide.
• Buoyancy – The ability of an object to float in water or air.
• Binary Fission – A way some single-celled organisms reproduce by splitting in two.
• Bar Magnet – A straight magnet with a north and south pole.
• Biodegradable – Something that can break down naturally and not harm the environment.
• Boiling – The process where a liquid turns into vapor at a specific temperature.
• Bond (Chemical) – A connection between atoms that forms molecules.

Science Words That Start with C

• Carbon – A chemical element found in all living things.
• Cell – The basic unit of life in all living organisms.
• Chemical – A substance made of atoms that can combine or react with others.
• Chlorophyll – The green substance in plants that helps them make food from sunlight.
• Circuit – A path that electricity flows through.
• Climate – The usual weather in a place over a long period of time.
• Condensation – The process of gas turning into a liquid.
• Conductor – A material that allows heat or electricity to pass through easily.
• Conservation – Protecting natural resources and the environment.
• Constellation – A group of stars that form a shape or pattern in the sky.
• Consumer – An organism that eats other plants or animals for energy.
• Crater – A round hole on the surface of a planet or moon, often made by an impact.
• Crust – The outer layer of Earth.
• Cytoplasm – The jelly-like fluid inside a cell that holds its parts in place.
• Carbon Dioxide – A gas we breathe out and that plants use to make food.
• Crystal – A solid with a regular pattern of atoms, often seen in minerals.
• Circuit Board – A flat piece in electronics that connects wires and parts.
• Calorie – A unit of energy found in food.
• Catalyst – A substance that speeds up a chemical reaction without being changed itself.
• Classification – The process of grouping things based on their similarities.
• Comet – A small space object made of ice and dust that orbits the sun.
• Celsius – A scale used to measure temperature, where water freezes at 0°.

Science Words That Start with D

• Data – Facts and information collected during experiments or observations.
• Decay – The process of breaking down or rotting, often in plants and animals.
• Decomposer – An organism that breaks down dead plants and animals, like fungi or bacteria.
• Density – How much mass is in a certain amount of space.
• Deposition – When wind or water lays down sediment in a new location.
• Desalination – The process of removing salt from seawater.
• Desert – A dry area with very little rainfall.
• Diffusion – The movement of particles from an area of high concentration to low concentration.
• Digestive System – The organs that break down food in the body.
• Dinosaur – A type of reptile that lived millions of years ago and is now extinct.
• Dissolve – When a substance mixes completely with a liquid.
• DNA – The material in cells that carries genetic information.
• Dormant – Not active at the moment, but able to become active later (like a sleeping plant or volcano).
• Drag – A force that slows down a moving object, often caused by air or water resistance.
• Drought – A long period with little or no rainfall.
• Dust – Tiny particles in the air or on surfaces, often studied in space or environmental science.
• Ductile – A property of materials that can be stretched into thin wires.
• Diversity – A variety or range of different things, often used in biology to describe life forms.

Science Words That Start with E

• Earth – The planet we live on, part of the solar system.
• Ecosystem – A community of living things and their environment working together.
• Electricity – A form of energy that powers lights, machines, and many devices.
• Electron – A tiny particle with a negative charge that moves around the nucleus of an atom.
• Element – A pure substance made of only one kind of atom, like oxygen or gold.
• Energy – The ability to do work or cause change.
• Evaporation – The process of a liquid turning into a gas.
• Erosion – The wearing away of land by wind, water, or ice.
• Equator – An imaginary line around the middle of the Earth that divides it into two halves.
• Evolution – The gradual change in living things over a long period of time.
• Exhale – To breathe out air from the lungs.
• Experiment – A test done to learn something or find out if an idea is correct.
• Extinct – When a plant or animal no longer exists anywhere on Earth.
• Eyepiece – The part of a microscope or telescope you look through.
• Exoskeleton – A hard outer shell that supports and protects some animals, like insects.
• Endangered – A species that is at risk of becoming extinct.
• Eclipse – When the moon or sun is hidden by another object in space.
• Elasticity – The ability of a material to return to its original shape after being stretched or compressed.
• Embryo – A developing organism in its early stages of growth.
• Environment – Everything around a living thing, including air, water, and land.

Science Words That Start with F

• Fahrenheit – A temperature scale where water freezes at 32° and boils at 212°.
• Fault – A break in Earth’s crust where earthquakes can happen.
• Fertilizer – A substance added to soil to help plants grow.
• Fiber – A thin thread-like material found in plants and some foods.
• Friction – A force that slows down or stops movement between two surfaces that touch.
• Fossil – The remains or marks of ancient plants or animals found in rock.
• Force – A push or pull that can change how something moves.
• Freezing Point – The temperature at which a liquid turns into a solid.
• Frequency – How often a wave repeats over a period of time.
• Fuel – A material used to produce energy, such as gas, coal, or oil.
• Fusion – A process where two atoms join together to form a new one and release energy.
• Fungus – A type of living thing like mold, mushrooms, or yeast.
• Formula – A math or science equation used to solve problems or explain ideas.
• Filtration – The process of removing solid particles from a liquid or gas using a filter.
• Fluid – A substance that flows, such as a liquid or gas.
• Flagella – Tiny tail-like structures that help some cells move.
• Flower – The part of a plant that produces seeds.
• Focal Point – The point where light rays meet after passing through a lens.
• Food Chain – A sequence that shows how energy moves from one living thing to another.
• Free Radical – A highly reactive molecule with an unpaired electron, often involved in chemical reactions.

Science Words That Start with G

• Galaxy – A large group of stars, gas, and dust held together by gravity.
• Gas – A state of matter that spreads out to fill any space, like air.
• Gene – A part of DNA that decides traits like eye color or height.
• Genetics – The study of how traits are passed from parents to offspring.
• Germination – The process of a seed starting to grow into a plant.
• Geology – The study of Earth, its materials, and its structure.
• Glacier – A large, slow-moving mass of ice.
• Gravity – The force that pulls objects toward each other, especially toward Earth.
• Greenhouse Effect – The warming of Earth’s surface due to gases trapping heat in the atmosphere.
• Groundwater – Water found under the Earth’s surface.
• Growth – The process of getting bigger or developing over time.
• Gyroscope – A spinning tool used to show direction or balance in machines.
• Gas Giant – A large planet made mostly of gases, like Jupiter or Saturn.
• Geothermal Energy – Heat energy from inside the Earth.
• Gizzard – A part of some animals’ digestive systems that grinds up food.
• Glucose – A simple sugar that provides energy to living things.
• Gradient – A gradual change in a property such as temperature or pressure.
• Genome – All the genetic material of an organism.
• Galvanometer – A tool used to detect and measure small electric currents.
• Gravity Well – A space region where gravity is strong, usually around a planet or star.

Science Words That Start with H

• Habitat – The natural home or environment of a living thing.
• Heat – A form of energy that makes things warm or hot.
• Herbivore – An animal that eats only plants.
• Heredity – The passing of traits from parents to offspring.
• Humidity – The amount of water vapor in the air.
• Hurricane – A powerful storm with strong winds and heavy rain.
• Hypothesis – A smart guess or prediction that can be tested in an experiment.
• Hydrogen – The lightest and most common element in the universe.
• Hydrosphere – All the water on Earth, including oceans, lakes, and rivers.
• Hibernation – A deep sleep some animals go into during winter to save energy.
• Helium – A light gas used in balloons and found in the atmosphere.
• Hybrid – The offspring of two different species or types, often in plants and animals.
• Hardness – How resistant a material is to being scratched or broken.
• Heat Energy – The energy of moving particles that causes temperature to rise.
• Heart – The organ that pumps blood through the body.
• Hydraulic – A system that uses liquid pressure to do work.
• Host – An organism that supports another organism, such as a parasite.
• Hormone – A chemical messenger in the body that controls growth and activity.
• Horizon – Where the Earth and sky appear to meet in the distance.
• Hemisphere – Half of a sphere, such as the northern or southern half of Earth.

Science Words That Start with I

• Ice – Frozen water, the solid form of H₂O.
• Igneous Rock – Rock formed from cooled lava or magma.
• Immune System – The body’s defense system against illness and infection.
• Immunity – Protection from disease, often after recovery or vaccination.
• Inclined Plane – A flat surface set at an angle to help lift objects more easily.
• Independent Variable – The part of an experiment that is changed on purpose.
• Inertia – The tendency of an object to stay still or keep moving unless acted on.
• Infrared – A type of light we can’t see, often used in heat sensors and remote controls.
• Inhale – To breathe in air.
• Insect – A small animal with six legs and three body parts, like a bee or ant.
• Insulation – A material that stops heat or electricity from passing through.
• Intensity – The strength or brightness of something, like light or sound.
• Interaction – How two or more things affect or respond to each other.
• Interdependence – When living things rely on each other to survive.
• Internal Organs – The parts inside a body that perform important functions.
• Ion – An atom that has gained or lost electrons and has a charge.
• Ionic Bond – A chemical bond formed when atoms transfer electrons.
• Iris – The colored part of the eye that controls how much light enters.
• Isotope – A version of an element with a different number of neutrons.
• Insulator – A material that resists the flow of heat or electricity.

Science Words That Start with J

• Joule – A unit used to measure energy, work, or heat.
• Jet Stream – A fast-moving current of air high in the atmosphere.
• Jellyfish – A soft, ocean animal with tentacles, often used in marine biology.
• Jupiter – The largest planet in our solar system, known for its Great Red Spot.
• Joint – The place where two bones meet in the body, allowing movement.
• Jawbone – The bone that forms the framework of the mouth and helps with chewing.
• Junction – A point where two or more things meet, such as in nerves or circuits.
• J-shaped Curve – A type of graph showing rapid growth, like in population studies.
• Juvenile – A young organism that has not yet reached adulthood.
• Justice (in environmental science) – Fair treatment and involvement of all people in environmental laws and policies.

Science Words That Start with K

• Kelvin – A temperature scale used in science, especially in physics.
• Kinetic Energy – The energy an object has because it is moving.
• Kaleidoscope – A tube with mirrors and colored shapes that create patterns when turned, often used to explain light and reflection.
• Karyotype – A picture showing all the chromosomes in a cell, used in genetics.
• Kidney – An organ in the body that removes waste from the blood.
• Kilogram – A unit used to measure mass (1 kilogram = 1,000 grams).
• Kilometer – A unit used to measure distance (1 kilometer = 1,000 meters).
• Kite – A simple example of flight used to explain wind, lift, and air pressure.
• Keratin – A strong protein found in hair, nails, and animal horns.
• Keystone Species – A species that has a big effect on its ecosystem; without it, the ecosystem would change a lot.
• Kaolin – A type of clay used in science and industry, especially in ceramics.

Science Words That Start with L

• Lab (Laboratory) – A place where scientific experiments and research are done.
• Lava – Melted rock that flows from a volcano.
• Light – A form of energy that helps us see and travels in waves.
• Liquid – A state of matter that flows and takes the shape of its container.
• Lungs – Organs in the body that take in oxygen and release carbon dioxide.
• Lens – A curved piece of glass or plastic that bends light to help us see better.
• Leaf – The part of a plant where photosynthesis takes place.
• Lever – A simple machine used to lift or move objects.
• Load – The object being moved or lifted, especially when using machines.
• Latitude – The distance north or south of the equator, measured in degrees.
• Luster – The way a mineral reflects light (e.g., shiny or dull).
• Lithosphere – The solid outer layer of Earth, including the crust and upper mantle.
• Life Cycle – The stages an organism goes through from birth to death.
• Lipid – A type of fat found in the body and in food.
• Lymph – A fluid that moves through the lymphatic system to help fight infection.
• Larva – A young form of an animal that looks different from the adult, like a caterpillar.
• Longitudinal Wave – A wave where the particles move back and forth in the same direction the wave travels.
• Limiting Factor – Something that controls the growth or survival of a population in an ecosystem.
• Light-Year – The distance light travels in one year, used in astronomy.
• Lichen – A simple plant made of algae and fungus that often grows on rocks or trees.

Science Words That Start with M

• Magnet – An object that attracts certain metals like iron.
• Magma – Hot, melted rock found beneath Earth’s surface.
• Mass – The amount of matter in an object.
• Matter – Anything that has mass and takes up space.
• Melting – The process of a solid turning into a liquid.
• Meteor – A small object from space that burns up in Earth’s atmosphere (also called a shooting star).
• Mitochondria – Parts of a cell that make energy.
• Mixture – Two or more things combined that can be separated easily.
• Molecule – Two or more atoms joined together.
• Moon – A natural object that orbits a planet, like Earth’s moon.
• Magnetism – A force that pulls or pushes certain materials, often seen in magnets.
• Motion – A change in the position of an object.
• Microscope – A tool used to see very small things that can’t be seen with the eyes alone.
• Mineral – A natural, solid substance found in the Earth.
• Mutation – A change in the DNA of a living thing.
• Mantle – The thick layer of Earth between the crust and the core.
• Meteorologist – A scientist who studies the weather.
• Melting Point – The temperature at which a solid becomes a liquid.
• Mammal – A warm-blooded animal with hair or fur that usually gives birth to live young.
• Magnetosphere – The area around a planet affected by its magnetic field.

Science Words That Start with N

• Nerve – A bundle of fibers that sends messages between the brain and body.
• Neutron – A particle in the nucleus of an atom with no electric charge.
• Nitrogen – A gas that makes up most of the air we breathe.
• Nucleus – The center of an atom or the control center of a cell.
• Nutrition – The process of taking in and using food for energy and growth.
• Niche – The role or job of an organism in its environment.
• Nebula – A cloud of gas and dust in space where stars may form.
• Newton – A unit of force in science, or the scientist who discovered the laws of motion.
• Nonrenewable Resource – A natural resource that cannot be replaced quickly, like coal or oil.
• Nymph – A young form of some insects that looks like a small adult but can’t reproduce.
• Natural Resource – Materials from nature that people use, like water, trees, and minerals.
• Noise Pollution – Harmful or annoying levels of sound in the environment.
• Nerve Cell (Neuron) – A type of cell that carries electrical signals in the body.
• Nucleotide – A building block of DNA and RNA.
• Nanotechnology – The science of building and using things at a very small (nano) scale.
• Nasal – Related to the nose or the nasal passage.
• Neutral – Not having a positive or negative charge.
• Nematode – A type of tiny roundworm often found in soil or water.
• Newton’s Laws of Motion – Three rules that explain how things move.
• Nocturnal – Active at night and resting during the day.

Science Words That Start with O

• Observation – Watching something carefully to gather information.
• Organism – Any living thing, such as a plant, animal, or microbe.
• Orbit – The path an object takes as it moves around another object in space.
• Oxygen – A gas in the air that humans and animals need to breathe.
• Omnivore – An animal that eats both plants and other animals.
• Organ – A part of the body that has a specific job, like the heart or lungs.
• Ozone – A gas found in Earth’s atmosphere that protects us from harmful sunlight.
• Oxidation – A chemical reaction where a substance combines with oxygen (like rusting).
• Ocean – A large body of salt water that covers much of Earth.
• Offspring – The young or babies produced by living things.
• Opaque – Not letting light pass through.
• Optics – The study of light and how it behaves.
• Osmosis – The movement of water through a membrane from one area to another.
• Organ System – A group of organs that work together to perform a function in the body.
• Orbitals – Areas around an atom where electrons are likely to be found.
• Oil – A liquid fossil fuel used for energy and found in Earth’s crust.
• Outcrop – A visible exposure of bedrock or ancient geological layers on the surface.
• Ohm – A unit used to measure electrical resistance.
• Optimum – The best or most favorable condition for something to happen.
• Obsidian – A dark, glass-like volcanic rock formed from cooled lava.

Science Words That Start with P

• Particle – A very small piece of matter.
• Photosynthesis – The process by which plants make food using sunlight.
• Precipitation – Water that falls from the sky as rain, snow, sleet, or hail.
• Planet – A large object that orbits a star, like Earth or Mars.
• Pollution – Harmful materials that dirty the air, water, or land.
• Protein – A nutrient that helps build and repair body tissues.
• Proton – A positively charged particle found in the nucleus of an atom.
• Physical Change – A change in matter that does not create a new substance.
• Potential Energy – Stored energy that an object has because of its position.
• Pressure – The force applied to a surface.
• Photosphere – The visible surface of the sun.
• Paleontology – The study of fossils and ancient life.
• Population – A group of the same kind of organisms living in one area.
• Pollinator – An animal, like a bee, that helps plants reproduce by spreading pollen.
• Phenomenon – An event or fact that can be observed and studied.
• Plasma – A state of matter like gas, but with charged particles; found in stars.
• Petal – The colorful part of a flower that attracts pollinators.
• Plate Tectonics – The theory that Earth’s surface is made of moving plates.
• Pathogen – A microorganism that causes disease.
• Pendulum – A weight hung from a point that swings back and forth.
• Permeable – Allows liquids or gases to pass through.
• Photosensitive – Reacts to light, often used to describe certain materials or organisms.
• Pupa – The stage in some insects’ life cycle between larva and adult, like a chrysalis in butterflies.

Science Words That Start with Q

• Quartz – A hard, crystal-like mineral found in many types of rocks.
• Quantum – A very small amount of energy in physics, often related to atoms.
• Quark – A tiny particle that makes up protons and neutrons.
• Quantity – An amount or number of something.
• Qualitative Data – Information that describes qualities, like color or texture.
• Quantitative Data – Information that uses numbers, like height or temperature.
• Quarantine – Keeping someone or something separate to prevent the spread of disease.
• Question – A part of the scientific method that helps start an investigation.
• Quasars – Extremely bright and distant objects in space powered by black holes.
• Quotient – The result of dividing one number by another, often used in science and math.

Science Words That Start with R

• Radiation – Energy that travels through space as waves or particles.
• Rain – Water droplets that fall from clouds to the ground.
• Reactant – A substance that starts a chemical reaction.
• Reactor – A machine where controlled chemical or nuclear reactions happen.
• Recycle – To process materials so they can be used again.
• Reflection – When light, sound, or heat bounces off a surface.
• Refraction – When light bends as it passes through different materials.
• Reproduction – The process by which living things make more of their kind.
• Resistance – The slowing down of electric current or motion.
• Respiration – The process of releasing energy from food, usually with oxygen.
• Resource – Something in nature that people use, like water or wood.
• Ribosome – A part of a cell that makes proteins.
• Rock – A solid material made of minerals, found in Earth’s crust.
• Rotation – The spinning of an object, like Earth turning on its axis.
• Radiology – The study and use of X-rays and other radiation in medicine.
• Rainforest – A dense forest with a lot of rainfall and many living things.
• Rare Earth Elements – A group of metals used in electronics and clean energy.
• Reptile – A cold-blooded animal with scales, such as a snake or lizard.
• Rust – A reddish coating that forms when iron reacts with oxygen and water.

Science Words That Start with S

• Solid – A state of matter with a definite shape and volume.
• Solution – A mixture where one substance is dissolved in another.
• Sound – Vibrations that travel through air or another medium and can be heard.
• Species – A group of similar living things that can reproduce together.
• Solar System – The sun and all the planets and objects that orbit it.
• Sun – The star at the center of our solar system that gives Earth light and heat.
• Sediment – Small pieces of rock or material that settle at the bottom of water.
• Sublimation – When a solid changes directly into a gas without becoming a liquid.
• Symbiosis – A close relationship between two different living things.
• Spectrum – A range of light waves or colors, often seen in a rainbow.
• Science – The study of the natural world using observation and experiments.
• Satellite – An object that orbits a planet, either natural (like the Moon) or man-made.
• Star – A giant ball of hot gas that produces light and heat, like the sun.
• Soil – The top layer of Earth where plants grow.
• System – A group of parts that work together as a whole.
• Sensor – A device that detects and measures physical properties like heat or motion.
• Salt – A compound made when an acid and base react, commonly used in food.
• Skeleton – The internal structure of bones in a living organism.
• State of Matter – The form something takes: solid, liquid, gas, or plasma.
• Static Electricity – A buildup of electric charge on the surface of something.

Science Words That Start with T

• Temperature – A measure of how hot or cold something is.
• Telescope – A tool used to see faraway objects in space.
• Tissue – A group of similar cells that work together in a body.
• Trait – A characteristic or feature of a living thing, like eye color.
• Tectonic Plates – Huge pieces of Earth’s crust that move and cause earthquakes.
• Test Tube – A small glass container used in science labs for experiments.
• Thermometer – A tool used to measure temperature.
• Transparency – The quality of letting light pass through clearly.
• Transpiration – The release of water vapor from plants through their leaves.
• Tornado – A fast-spinning column of air that touches the ground, often during storms.
• Toxin – A poisonous substance made by living things like bacteria or plants.
• Turbine – A machine with spinning blades that creates energy, often used in power plants.
• Tundra – A cold, treeless region with frozen ground, often found in the Arctic.
• Thrust – A force that pushes something forward, like in rockets or planes.
• Thermal Energy – Energy that comes from heat.
• Thigmotropism – A plant’s response to touch, like vines wrapping around objects.
• Typhoon – A powerful storm like a hurricane, usually found in the Pacific Ocean.
• Tropism – The way plants grow in response to things like light or gravity.
• Tissue Culture – Growing cells or tissues in a lab for study or experiments.
• Technology – The use of science to solve problems and create tools or systems.

Science Words That Start with U

• Ultraviolet (UV) – A type of invisible light from the sun that can cause sunburn.
• Universe – Everything that exists, including all space, matter, and energy.
• Uranium – A heavy metal used as fuel in nuclear power plants.
• Urine – A liquid waste removed from the body by the kidneys.
• Umbra – The darkest part of a shadow, especially during an eclipse.
• Urethra – The tube that carries urine out of the body.
• Uterus – The organ in female mammals where babies grow before birth.
• Uniform Motion – Movement at a constant speed in the same direction.
• Unbalanced Force – A force that causes a change in motion.
• Ultrasound – Sound waves used in medicine to see inside the body.
• Upwelling – The movement of deep, cold water to the ocean’s surface, bringing nutrients.
• Uplift – The rising of land, often caused by tectonic activity.
• Urea – A chemical waste made by the body and removed in urine.
• Ultramicroscope – A microscope that allows scientists to see extremely small particles.
• Ubiquitous – Present everywhere; used in science to describe things found in many places (like bacteria).

Science Words That Start with V

• Vaccine – A substance that helps protect the body from disease by training the immune system.
• Vacuum – A space with no air or matter.
• Variable – Something that can change in an experiment.
• Vapor – A substance in its gas form, especially water in the air.
• Vein – A blood vessel that carries blood back to the heart.
• Velocity – The speed of something in a specific direction.
• Vertebrate – An animal with a backbone, like a fish, bird, or human.
• Vibration – A fast back-and-forth movement that can create sound.
• Virus – A tiny germ that can cause illness and needs a host to reproduce.
• Viscosity – How thick or sticky a liquid is (like honey has high viscosity).
• Voltage – The force that pushes electric current through a wire.
• Volume – The amount of space something takes up.
• Vulcanology – The study of volcanoes and related processes.
• Vacuole – A storage area in a cell for food, water, or waste.
• Valve – A part that controls the flow of liquids or gases in a system.
• Vector – In science, it can mean a quantity with direction and magnitude, or an organism that spreads disease (like a mosquito).
• Vine – A plant with long stems that can climb or spread.
• Villi – Tiny finger-like parts in the small intestine that absorb nutrients.
• Volt – A unit for measuring electric potential (voltage).

Science Words That Start with W

• Water – A clear liquid that all living things need to survive.
• Weather – The condition of the atmosphere at a certain time and place (like rain, sun, wind).
• Wind – Moving air caused by differences in temperature and pressure.
• Weight – The force of gravity pulling on an object.
• Wavelength – The distance between two waves, such as in light or sound.
• Waxing – When the visible part of the moon is getting larger.
• Waning – When the visible part of the moon is getting smaller.
• Wave – A repeating movement that carries energy, like sound or light waves.
• Warm-blooded – Animals that keep a constant body temperature, like mammals and birds.
• Water Cycle – The movement of water through evaporation, condensation, precipitation, and collection.
• Watershed – An area of land where all the water drains into the same place.
• Work – In science, using force to move something over a distance.
• Wheel and Axle – A simple machine that helps lift or move things.
• Worm – A simple, soft-bodied animal, often used in life science studies.
• Watt – A unit for measuring power or the rate of energy use.
• Weathering – The breaking down of rocks by wind, water, or ice.
• Wing – A body part or structure that helps animals or machines fly.
• Wetland – Land that is covered with shallow water, like swamps or marshes.

Science Words That Start with X

• X-ray – A type of invisible energy that can pass through objects and is used to see inside the body.
• Xylem – The part of a plant that carries water from the roots to the leaves.
• Xenon – A colorless, odorless gas used in lights and medical imaging.
• Xerophyte – A plant that can live in very dry places, like a cactus.
• X-chromosome – One of the two sex chromosomes that determine a person’s gender.
• X-axis – The horizontal line on a graph.
• Xenobiotic – A chemical that is not naturally found in the body or environment.
• Xenotransplant – The transplant of an organ or tissue from one species to another.
• Xenogenesis – The supposed production of offspring that are unlike the parent organism (a historical/scientific term, rarely used today).
• Xanthophyll – A yellow pigment found in leaves that helps with photosynthesis.

Science Words That Start with Y

• Yeast – A tiny fungus used in baking and brewing that helps things rise by producing gas.
• Yolk – The yellow part of an egg that contains nutrients for a growing embryo.
• Yttrium – A chemical element used in electronics and lasers.
• Y-axis – The vertical line on a graph.
• Young – The offspring or babies of animals or people.
• Yield – The amount of product made in a scientific process or chemical reaction.
• Yawn – A reflex that brings more oxygen into the lungs, sometimes studied in biology.
• Y-Chromosome – One of the two sex chromosomes that helps determine male biological traits.

Science Words That Start with Z

• Zinc – A metal and essential mineral used by the body and in various chemical reactions.
• Zoology – The study of animals and their behavior, structure, and classification.
• Zygote – A fertilized egg cell formed when sperm and egg join.
• Zone – A specific area with certain features, such as climate zones or time zones.
• Zooplankton – Tiny floating animals in water that are an important part of the food chain.
• Zero Gravity – A condition in which there is little or no gravitational force, often in space.
• Zonation – The way different types of life are arranged in layers or zones, such as in a forest or ocean.
• Zymology – The study of fermentation processes, like in bread or yogurt making.
• Zeolite – A mineral used in water purification and chemical separation.