Basic Science Definitions

Science lesson in classroom

Half the battle in finishing any assignment for science is figuring out what you are reading. This handy list of basic science terms, culled from the University of Berkeley science glossary, can help you get through any homework assignment or project, big or small.

Experimental Design

So you're tasked with doing a science project with a control and variables. These terms are basic to any experiment you design.

  • Control - The factor in an experiment that does not change. Having a control allows you to measure your results so that you know how much a variable has changed in an experiment.
  • Data - The information you gather in your experiment.
  • Experiment - The test you perform to see if your hypothesis is correct or incorrect.
  • Hypothesis -Your best guess at how an experiment is going to turn out. The trick to writing a good hypothesis is to make sure that it is testable and has a concrete answer.
  • Procedure - The steps you use in your experiment.
  • Qualitative Observation - Using words to describe something that you are seeing in your experiment.
  • Quantitative Observation - Using numbers to describe something that you are seeing in your experiment.
  • Variable - A variable is any aspect of an experiment that can be measured, controlled or changed. If the variable is something you are changing to test your hypothesis, the variable is independent. If the variable is a change you are measuring, it is a dependent variable.


Teacher and student

Generally, biology is one of the first sciences you study as a student. These are the literal building blocks for most of your scientific inquiries.

  • Cell - The smallest part of an organism.
  • Chlorophyll - Chlorophyll is the green pigment found in various plants, responsible for trapping light and "feeding" the plant during photosynthesis.
  • Enzymes - Catalysts for biological processes, enzymes control specific functions in the body.
  • Evolution - The process by which species change to adapt to their environment.
  • Habitat - The environment in which a species is typically found.
  • Invertebrate - Invertebrates are animals with no backbone. Invertebrates include organisms like protozoa, annelids (worms), arachnids (spiders), mollusks, echinoderms, crustaceans and other insects.
  • Mitochondria - Small parts of a cell (organelles) that convert glucose into energy.
  • Natural Selection - The process by which animals within a species that possess less desirable traits for survival die off, thereby leaving the animal with more desirable traits. Over time, this process helps explain how a species might evolve.
  • Nucleus - Organelle that contains the chromosomes. It is often referred to as the 'brain' of a cell because it contains the genetic instructions.
  • Organelles - Small parts of cells that each have a specific purpose. For example, the mitochondria and nucleus are both organelles.
  • Pathogen - A disease-causing agent.
  • Photosynthesis - This is the process plants use to convert sugar and carbon dioxide into energy. One byproduct of photosynthesis is oxygen.
  • Respiration - Living organisms use respiration to produce energy. Typically, respiration involves the intake of oxygen and the production of carbon dioxide.
  • Vertebrate - Vertebrates are animals with backbones. Vertebrates include fish, birds, mammals (including people), amphibians and reptiles.


Rainbow DNA

Still a part of the study of biology, you will find these terms often as you study how organisms reproduce and inherit traits.

  • Allele - A different form of a gene, responsible for genetic variance. Some genes have a variety of different alleles, located on the same gene in the same spot on each chromosome.
  • Chromosomes - DNA molecules that contain the set of instructions required to build a cell.
  • Dominant Trait - The relationship between two alleles in which one masks the expression of the other.
  • Gene - A unit of inheritance. (Genome is the collective noun used for a set of genes.)
  • Genotype - The genetic makeup of an individual.
  • Heredity - The transfer of traits from one generation to the next.
  • Heterozygous - Referring to a person carrying genetic material for both possible traits.
  • Homozygous - Referring to a person carrying genetic material for a single trait. When a parent is homozygous, the offspring will inherit said trait.
  • Mutation - An alteration in the genetic code which produces a new or differing trait.
  • Phenotype - The observable characteristics of an individual.
  • Punnet Square - A simple graph to show all the possible combinations of offspring genotypes that could occur between two parents.
  • Recessive Trait - When two alleles of the same gene expression are present. Since there is no dominant trait involved, there is nothing to mask the expression of the recessive trait.
  • Reproduction - The process by which a new organism is produced.
  • Zygote - A zygote is the term for a fertilized ovum.


Experiment in science class

Chemistry is a term-heavy topic. These basic terms will help get you through any homework you have.

  • Absolute zero - Theoretically, absolute zero is the lowest temperature possible. At this temperature, all molecular activity would cease.
  • Acid - An acid is lower than 7 on the pH scale, turns blue litmus paper red, is sour to taste, and yields hydrogen ions in an aqueous (water-based) solution. (Citrus fruit and vinegar are both acids.)
  • Atomic number - This is the number of protons in an atom. On the periodic table of elements, this number is located above the element symbol. For example, the atomic number for Hydrogen is 2.
  • Atomic symbol - The atomic symbol is the letter you see representing each element on the periodic table.
  • Atomic weight - The atomic weight is the average weight of an atom. This number is often underneath the atomic symbol on the periodic table of elements, however, not all periodic tables show this information.
  • Base - A base is higher than 7 on the pHscale and turns red litmus paper blue. In water, they usually feel slimy or slippery. Examples of bases include things like lye (for soap making), Tums or milk of magnesia.
  • Boiling point - The exact temperature at which a liquid turns to vapor.
  • Bond - A chemical link between atoms.
  • Catalyst - Technically, a catalyst reduces the activation energy of a reaction. In laymen's terms, a catalyst is the substance that makes a reaction happen.
  • Electrons - Atomic particles with a negative charge.
  • Element - An element is composed of atoms that all have the same atomic number. For example, hydrogen and oxygen are both elements.
  • Evaporation - When a substance changes from liquid to gas below its boiling point.
  • Freezing Point - The exact temperature at which liquid turns to solid.
  • Mass - The quantity of matter in a body.
  • Molecule - A molecule is the smallest part of something that retains the chemical properties of the whole. For example, a water molecule is made up of two hydrogen atoms and one oxygen atom.
  • Neutrons - Atomic particles with no electric charge.
  • Nucleus - That part of an atom containing the protons and neutrons.
  • pH Scale - Technically, the pH scale measures hydrogen ion concentration. If a substance rates higher than a 7 on the pH scale, it is considered a base. If a substance rates higher than 7 on the pH scale, it is considered an acid. Pure water would rate a 7 on the pH scale.
  • Protons - Atomic particles with a positive charge.
  • Salt - In chemical terms, salt is the result of a neutralizing reaction between an acid and a base.
  • Temperature - How hot one body is when compared to another.

Earth Science

Girl with balloon

The study of the earth is not only an important science in school, but you'll also run across these terms a lot as you read the news.

  • Atmosphere - The layer of gasses around a given planet.
  • Climate - A region's climate describes the average weather conditions over time. For example, a tropical climate is generally humid and hot, with rainy seasons.
  • Constellation - A constellation is a group of stars that appear to make a pattern in the sky.
  • Core - The innermost layer of the earth.
  • Eclipse - The partial or complete blocking of one object by another as in a lunar or solar eclipse.
  • Galaxy - A galaxy is a giant structure containing billions of stars.
  • Hydrologic or water cycle - The cycle that describes how water moves from the ocean to the atmosphere to the land and back to the ocean.

  • Milky Way - The galaxy where Earth is located.

  • Plate tectonics - The theory that the earth's crust is broken into several large pieces and are floating on a semi-molten mantle.
  • Renewable resources - Renewable resources are resources that can renew themselves. A few examples include solar energy, fresh water and oxygen.
  • Solar system - The sun and the bodies that orbit around it.


Blackboard with formulas

Physics is the branch of science that explains phenomenon you see and work with every day. Physics explains things like falling, or how an airplane flies. Being such a big part of everyday life, it's important to make sure that you understand its basic terms.

  • Acceleration - Commonly mistaken by students as 'speeding up,' acceleration is actually the rate of change in velocity. (By this definition, you can have positive or negative acceleration.)
  • Density - The mass of an object divided by its volume.
  • Electric current - The flow of electrons through a conductor.
  • Energy - The capacity to do work.
  • Fission - Splitting the nucleus and atom into smaller parts.
  • Force - An action that will accelerate a body in the direction of the applied force.
  • Friction - How surfaces interact with one another or the measure of resistance felt when one surface slides against another.
  • Fusion - The joining together of two atomic nuclei.
  • Gravity - The attraction that all bodies have for one another.
  • Half-life - The time it takes for the level of radioactivity in an element to be cut in half.
  • Inertia - The law of inertia is also Newton's first law of motion. Inertia is the tendency for a body to stay at rest when it is at rest, or to keep moving if it is moving, unless an outside force acts upon said body.
  • Kinetic energy - Kinetic energy is the energy something has when it's in motion.
  • Lens - A lens modifies light. Convex lenses focus light while concave lenses diffuse light.
  • Light - Light is the visible part of the electromagnetic spectrum. White light is a combination of all the above colors.
  • Magnet - A body which produces a magnetic field. All magnets are di-pole and follow the rule that poles that are alike repel, but poles that are unlike attract.
  • Momentum - The product of mass times velocity.
  • Newton's Laws of Motion: These are basic laws of physics that help scientists predict the path of an object. They are:
    • A body at rest tends to stay at rest; a body in motion tends to stay in motion.
    • The acceleration of a body is proportional to the applied force. This is expressed by the universal formula: Force = mass × acceleration.
    • For every action, there is an equal and opposite reaction.
  • Potential Energy - Amount of useable energy within a body at rest.
  • Strain - The deformation of a body under an applied load.
  • Stress - The measure of a force acting on a body.
  • Torque - The tendency of a body to rotate under an applied force..
  • Velocity - The rate of change of distance with respect to time.
  • Viscosity - Students often think viscosity is how thick a liquid is. However, it is correctly defined as the internal friction of a fluid. Thick fluids have a high viscosity whereas thin fluids have a low viscosity.
  • Weight - The gravitational force exerted on a mass.
  • Work - In physics, work is when a force is applied to an object to make it move. You could also define work as energy transferred to a system.

Create a Glossary and Memorize the Terms

Knowing basic terms will help any science class homework go much more easily. To learn the terms quickly, note the terms you do not know, and work on memorizing them by making flashcards and reviewing consistently.

Basic Science Definitions