100 Essential Scientific Terms

Below is a comprehensive list of scientific terms categorized into different branches of science. These terms are essential for understanding basic scientific concepts and communicating effectively in the field of science.

1. Scientific Method & Inquiry

• Observation: Using your senses to gather information.
• Hypothesis: A testable guess or prediction.
• Experiment: A test to find out if your hypothesis is correct.
• Variable: Something that can change in an experiment.
• Independent Variable: The one thing you change in an experiment.
• Dependent Variable: What you measure in an experiment.
• Control: The part of an experiment that stays the same for comparison.
• Data: Information collected during an experiment.
• Conclusion: A summary of what you learned from an experiment.
• Theory: A well-tested explanation that fits many observations.
• Law: A rule that describes a pattern in nature.
• Evidence: Facts or data that support a conclusion.
• Model: A representation of something too big, small, or complex to study directly.
• Prediction: A guess about what might happen based on evidence.
• Analyze: To examine data carefully to understand it.

2. Physical Science (Physics & Chemistry)

Matter & Its Properties

• Atom: The smallest unit of an element.
• Molecule: Two or more atoms bonded together.
• Element: A pure substance made of only one kind of atom.
• Compound: A substance made of two or more elements chemically combined.
• Mixture: A combination of substances that aren’t chemically joined.
• Solid: Matter with a fixed shape and volume.
• Liquid: Matter with a fixed volume but no fixed shape.
• Gas: Matter with no fixed shape or volume.
• Plasma: A high-energy state of matter found in stars and lightning.
• Density: How much mass is in a given volume of a substance.

Chemical Properties & Reactions

• Physical Change: A change that doesn’t form a new substance (like melting).
• Chemical Change: A change that forms one or more new substances.
• Reactant: A substance that starts a chemical reaction.
• Product: A substance made during a chemical reaction.
• Conservation of Mass: Matter can’t be created or destroyed in a reaction.
• Periodic Table: A chart that organizes all known elements.
• Proton: A positively charged particle in an atom’s nucleus.
• Neutron: A particle with no charge in the nucleus of an atom.
• Electron: A negatively charged particle outside the nucleus.
• Ion: An atom that has gained or lost electrons.
• pH: A scale that shows how acidic or basic a substance is.
• Acid: A substance with a pH below 7; tastes sour.
• Base: A substance with a pH above 7; tastes bitter and feels slippery.

Motion & Forces

• Force: A push or pull on an object.
• Gravity: The force that pulls things toward each other, especially Earth.
• Friction: A force that resists motion between two surfaces.
• Mass: The amount of matter in an object.
• Weight: The force of gravity on an object.
• Speed: How fast something is moving.
• Velocity: Speed in a specific direction.
• Acceleration: A change in speed or direction.
• Inertia: An object’s resistance to change in motion.
• Newton’s Laws: Three laws that describe how objects move.

Energy

• Energy: The ability to do work or cause change.
• Kinetic Energy: Energy of motion.
• Potential Energy: Stored energy due to position or condition.
• Thermal Energy: Energy from the motion of particles (heat).
• Electrical Energy: Energy caused by moving electric charges.
• Chemical Energy: Energy stored in chemical bonds.
• Renewable Energy: Energy from sources that can be reused (like solar).
• Nonrenewable Energy: Energy from sources that can run out (like coal).
• Conduction: Heat transfer through direct contact.
• Convection: Heat transfer through fluids moving.
• Radiation: Heat transfer through waves or rays (like sunlight).

3. Life Science (Biology)

Cells & Genetics

• Cell: The basic unit of life.
• Nucleus: The control center of a cell that holds DNA.
• Mitochondria: The part of a cell that makes energy.
• Cytoplasm: The jelly-like substance inside a cell.
• Cell Membrane: The outer layer of a cell that controls what goes in and out.
• DNA: A molecule that contains genetic information.
• Chromosome: A structure in the nucleus that holds DNA.
• Gene: A part of DNA that determines traits.
• Mitosis: Cell division that makes two identical cells.
• Meiosis: Cell division that makes sex cells with half the DNA.
• Heredity: Passing traits from parents to offspring.
• Trait: A feature or characteristic passed down from parents.

Organisms & Systems

• Organism: A living thing.
• Tissue: A group of similar cells working together.
• Organ: A part of the body made of tissues that does a job.
• Organ System: A group of organs working together.
• Homeostasis: The body’s way of keeping balance.
• Circulatory System: Moves blood through the body.
• Respiratory System: Takes in oxygen and removes carbon dioxide.
• Digestive System: Breaks down food for the body to use.
• Nervous System: Sends signals between the brain and the body.
• Reproductive System: Helps organisms make offspring.

Ecology & Environment

• Ecosystem: A community of living and nonliving things in an area.
• Habitat: The natural home of a living thing.
• Population: All the members of one species in an area.
• Community: All living things in an ecosystem.
• Producer: A living thing that makes its own food (like plants).
• Consumer: A living thing that eats other organisms.
• Decomposer: A living thing that breaks down dead matter.
• Food Chain: Shows how energy moves from one organism to another.
• Food Web: A group of connected food chains.
• Biodiversity: The variety of life in an area.
• Adaptation: A trait that helps a living thing survive.
• Symbiosis: A close relationship between two different species.

4. Earth & Space Science

• Rock Cycle: The process of rocks changing from one type to another.
• Erosion: The movement of soil or rock by wind, water, or ice.
• Weathering: The breaking down of rocks into smaller pieces.
• Plate Tectonics: The theory that Earth’s surface is made of moving plates.
• Earthquake: The shaking of the ground caused by moving plates.
• Volcano: An opening in Earth’s surface that releases lava and gases.
• Fossil: The preserved remains or traces of ancient organisms.