Listed below is a collection of some of the most important science vocabulary words used in our class. This page is updated periodically, so be sure to refresh your browser every now and then. If you don’t see a word you are looking for, try visiting Merriam-Webster’s Learner’s Dictionary, a dictionary for younger science students.

 ABCD | EFG | HIJK | LMNOP | QRS | TUV | WXY&Z | Root Words | 123s


  • ACID: an acid is a chemical substance that donates or gives up protons (hydrogen ions) and/or accepts electrons.
  • ACIDIC: refers to an liquid (aqueous) solution having a pH less than 7.
  • AIR: a mixture of many different types of gases that surround the Earth and form the atmosphere. In our class, we will talk mostly about four of the gases found in air: nitrogen (N2), oxygen (O2), carbon dioxide (CO2), and water vapor (H2O).  However, always remember that air is a mixture of more than four gases.
  • ALKALINE: refers to an aqueous (liquid) solution having a pH greater than 7. Also known as “basic.”
  • ANIMALS: a living organism that consumes substances that either are living or were once living. Animals typically have specialized sense organs (for example, eyes), a nervous system, and are able to respond to stimuli in their environment.
  • ANNUAL PLANT: a plant in which the entire life cycle is completed in a single growing season.
  • ANTHER: the tip of the stamen.  It produces and bears the pollen.
  • ARTHROPODS: an arthropod is an invertebrate animal having an exoskeleton, a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda, and include the insects, arachnids, and crustaceans.
  • ATOM: the smallest unit of an element having all the characteristics of that element.  For example, in theory a single atom of gold still has all of the characteristics of a bar of solid gold, which probably consists of millions (or billions!) of atoms.
  • ATMOSPHERE: the envelope of gases surrounding the earth or another planet.


  • BASE: in chemistry, a base is a chemical substance that donates electrons (or hydroxide ions) or accepts protons.
  • BASIC: in chemistry, basic refers to an aqueous solution having a pH greater than 7. Also known as “alkaline.”
  • BIENNIAL PLANT: a plant requiring two growing seasons to complete its life cycle. Vegetative growth occurs the first year and flowering and fruiting occur during the second year.
  • BIOLOGICAL: of or related to…life and living processes.
  • BIOLOGY: the study of life and living processes.
  • BIOMASS: the mass of material derived from the living (or recently living) organisms found in a defined area. Biomass can be measured by any instruments that typically measure the mass of objects. For example, a pile of cut grass (recently living organisms) sitting in a backyard (a defined area) would contain a certain amount of measurable biomass (which could be measured using an electronic balance in either grams or kilograms!).
  • BIOMES: the main ecological regions into which the land surface can be divided.  Each biome has its own characteristic seasons, day length, rainfall pattern and maximum and minimum temperatures.  Some of the major biomes include tundra, coniferous forest, deciduous forest, tropical forest, temperate grassland, savanna (tropical grassland), scrubland, mountains, desert, and ice.  Most are named after the dominant vegetation, since this is key in determining the presence of other living things.  Each biome is a giant habitat (or macrohabitat).
  • BIOSPHERE: the regions of the surface, atmosphere, and hydrosphere of the earth (or analogous parts of other planets) occupied by living organisms.


  • CARBON: a chemical element with symbol C and atomic number 12. It is one of the 92 naturally occurring elements on Earth. A single carbon atom typically contains 6 protons, 6 neutrons, and 6 electrons.
  • CARNIVORE: an animal that feeds on flesh of another animal.
  • CELL: from the Latin word cella (meaning “small room”), cells are the basic structural, functional, and biological unit of all known living organisms. A cell is the smallest unit of life that can replicate independently, and cells are often called the “building blocks of life.”
  • CELL WALL: a rigid layer of complex sugars (polysaccharides) lying outside of the plasma membrane of the cells of plants, fungi, and bacteria. In the algae and higher plants it consists mainly of cellulose.
  • CHEMICAL: of or related to…reactions involving changes in atoms or molecules.
  • CHLOROPHYLL: a molecule (or green-colored pigment) present in all green plants and in cyanobacteria, which is responsible for the absorption of light to provide energy for photosynthesis. A single molecule of chlorophyll has the general chemical formula, C55H72O5N4Mg.
  • CHLOROPLAST: an organelle within green plant cells containing chlorophyll and in which photosynthesis takes place.
  • CILIARY MUSCLE: a muscle connected to the (eye) lens by ligaments called “suspensory ligaments.” They adjust the shape of the lens by contracting or relaxing, which makes the lens more or less curved. Changing the curve of the lens increases or decreases the refraction (redirection) of light.
  • COMPOUND: a substance that is composed of two or more separate elements found on the periodic table of elements. Sometimes, however, a compound is also defined simply as a “mixture” or “any substance that can be split up into simpler substances.”
  • CONSUMER: any organism that generally obtains food by feeding on other organisms because they lack of the ability to manufacture their own food.
  • COOL
  • CORNEA: a convex, tough, transparent (clear) window at the front of the eye. The cornea covers and protects the iris and the pupil. It refracts (redirects) light as it enters the eye. It plays an important role in focusing vision.
  • COTYLEDON (or SEED LEAF): the leaf of the embryo or seedling.  It contains food (e.g., starch) that the young plant can use as a source of energy.
  • CYST: a tough (strong) protective capsule.


  • DECOMPOSE: in our science classes, we usually use this word in reference to a dead body and/or to other material that was once considered living (i.e., organic). When such bodies or materials become rotten, we say they “decay” or “decompose.” This basically means to be broken down into smaller portions of matter.
  • DECOMPOSER: a decomposer is any living thing or organism–but especially a soil bacterium, fungus, or invertebrate–that decomposes organic material (see decompose above).
  • DICOTYLEDON: a plant whose embryo has two cotyledons.  This word is often abbreviated as “dicot.”
  • DENSITY: a material’s density is often defined as its “mass per unit volume.” In simpler terms, density is a measurement of how tightly matter is crammed together into a finite (bounded) amount of space.
  • DISSOLVE: to cause a solute–whether solid, liquid, or gas–to ‘pass’ into solution. We might think of ‘passing into solution’ as the solute–again, whether solid, liquid, or gas–being distributed somewhat evenly throughout the solution.
  • DORMANT CYST: a tough (strong) protective capsule enclosing a resting organism, such as a brine shrimp.
  • DRY MASS: the mass of an object–or sample of an object–when it is completely dry. In other words, it is the mass of the object after the entire concentration of water has been effectively removed from it. Dry mass is sometimes known as dry weight or dry matter.
    • Compared to the measurement known as wet mass (or fresh mass)–which includes the mass of the water–dry mass is typically more reliable for comparisons because the concentration of water inside of living tissue can vary/change so much.

ABCD | EFG | HIJK | LMNOP | QRS | TUV | WXY&Z | Root Words | 123s

 Last updated: September 2017


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