5th Grade Glossary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

abdomen	The end part of an insect's body, which contains the digestive and reproductive organs.
addiction	Physical dependence on a habit-forming substance.
astronaut	A person trained to go up in a space craft.
accelerate	To increase speed
animal	A many-celled organism which eats other living or once-living things and can move about at one point in its life. The cells of an animal have nuclei. One of the main kingdoms of living things.
arthropod	An invertebrate with a segmented body, jointed legs, and a hard outer shell called an exoskeleton. Includes insects, crustaceans, and arachnids.
atom	The smallest possible particle of matter. Anything smaller than an atom is just energy, not matter.
atomic number	The number of protons in the nucleus of an atom. The atomic number is what decides the chemical properties of an element.
axon	The branch of a neuron (a nerve cell) which sends messages to other neurons.
bacteria	Another name for monerans: A kingdom of single-celled organisms which do not have a nucleus
ball-and-socket joint	A joint in which a knob or ball on the end of one bone fits into a socket, and allows movement in many directions. Found in the shoulder and hip.
bivalve	The class of mollusks which includes clams, mussels, and oysters. The members of this class have two shells.
capsule	A small pressurized compartment.
cardiac muscle	Type of involuntary muscle found in the heart.
cartilage	A flexible rubbery tissue, which covers and protects the ends of the bones. Also found in the ear and the tip of the nose.
cell	The basic part of every living thing on earth.
cell membrane	A layer which surrounds and protects the outside of the cell
cephalopod	The class of mollusks which includes octopuses and squid. They have either no shell or an interior shell (in the case of squid). The word means "head foot."
chemical bond	When two molecules share or lend an electron, they are joined in a chemical bond.
chemical change	A change in matter where new molecules are formed.
chemical formula	A combination of chemical symbols which stands for the name of a molecule.
chemical symbol	A one- or two-letter symbol which stands for the name of an element. The first letter must be upper case. If there is a second letter, it must be lower case.
chemist	A scientist who studies matter, how it is put together, what it is made of, and how it acts.
chemistry	The science which studies matter and how it changes.
class	One of the main divisions of a phylum.
classification	Sorting things into groups with similar traits.
closed fracture	A fracture in which the bones do not go through the skin.
colony	A group of the same kind of organisms living and growing together
compact bone	The dense, hard outer part of a bone.
compound	A substance which has its own properties but which can be broken down into other substances. A compound is made of only one kind of molecule. Chemists break down compounds using special chemical methods which may include heat, electricity, and adding other substances to the compounds.
cosmonaut	An astronaut of the Soviet or Russian space program
cramp	What happens when muscles contract strongly and painfully.
cytoplasm	The jelly-like material on the inside of the cell. It contains many parts which keep the cell alive.
dendrite	A branch of a neuron (nerve cell) which receives messages from other cells.
drug	A chemical taken into the body which causes changes in the body.
drug abuse	The excessive use of drugs.
echinoderm	A phylum of small, slow, spiny-skinned animals with no brain, often with five-pointed star designs. They live underwater and have a stiff inside skeleton.
electron	The tiny subatomic particles which move in clouds at different energy levels around the outside of the atom. They have a negative charge. Electrons can be traded or shared with other atoms.
element	Substances which are the basic building blocks of all matter. An element is made of only one kind of atom. There are 110 known elements.
evolution	The change in groups of living things which happens over long periods of time, causing new species to appear.
exoskeleton	The hard outer body covering of arthropods.
experiment	A carefully controlled test, made to see if a hypothesis is correct.
family	One of the divisions of the classification of living things. Orders are divided into families, which are groups of genera.
fixed joint	a joint where two or more bones come together and do not allow any movement. Found in the skull.
fracture	A crack or break in a bone.
fruiting body	The part of a fungus which makes and releases spores. Example: mushroom
gastropod	The class of mollusks which includes snails and slugs. They have one shell (or no shell, in the case of slugs). The word means "stomach foot."
genus	A group of similar species (plural genera)>
gland	Organs or tissues in the body which make and release chemicals.
hermaphrodite	An organism which is both male and female at the same time. Comes from the names of the Greek gods Hermes (who was male) and Aphrodite (who was female).
hinge joint	A joint between two bones which allows them to move back and forth, like the hinge in a door. Found in the elbow and knee.
hormone	Chemicals released by glands.
host	The organism on which a parasite lives.
hyphae	The threadlike parts which make up a many-celled fungus.
hypothesis	An if-then statement of what should happen, based on an inference. For example, a hypothesis is: "If the temperature of water is lowered below zero degrees Celsius, then the water should turn to ice."
inference	An explanation for an observation.
invertebrate	An animal without a backbone.
involuntary muscle	A type of muscle which is not controlled by the conscious mind. Found in the walls of organs and in the heart.
joint	A place where two or more bones come together in the body.
kingdoms	One of five large groups into which scientists have classified all living things. (Currently, scientists are discussing whether there ought to be seven kingdoms instead.)
larva	Newly hatched young of any animal in which the young are very different in appearance from the adults. Plural: larvae.
ligament	Strong bands of tissue which hold bones together at a joint.
mantle	The part of a mollusk's body which covers most of the organs. It also makes the shell.
many-celled organism	An organism which is made of many cells, and usually has many different types of cells.
maneuver	A controlled change in movement or direction.
marrow	The soft tissue which fills the inner space in bones. It makes red blood cells and many white blood cells.
mass	The amount of matter in something. Mass can be measured with a balance or scale. Although it is related to weight, it is not exactly the same as weight.
matter	Anything that takes up space (has volume) and has mass. All matter is made of atoms.
mixture	A combination of different kinds of matter, in which the different kinds are not changed by being put together. Therefore, the parts of a mixture can be separated by physical methods, using the properties of the substances.
moderation	Not doing too much and not doing too little. Just doing just the right amount.
module	A part of a spacecraft which does a task and is complete in itself. Examples: command module and instrument module
molecule	Two or more atoms held together by a chemical bond. Just as an element is made of only one kind of atom, a compound is made of only one kind of molecule.
molt	To shed the outer body covering.
motor nerve cells	Messenger nerve cells which send signals to the muscles.
multi-stage	Having two or more rockets, used one after another.
mycelium	The name for the whole collection of hyphae of an individual fungus.
nerve	A bundle of nerve cells.
nervous system	The organ system made up of the brain, spinal cord, and the nerves.
neuron	A nerve cell.
neuroscientist	A scientist who studies the nervous system.
neurotransmitter	A chemical in the brain which carries messages between the neurons.
neutron	A subatomic particle with no charge located in the nucleus of an atom.
nucleus (atomic)	The center part of an atom, where the neutrons and protons are located. The nucleus contains most of the mass of the atom.
nucleus (cell)	The center part of a cell. The nucleus contains most of the DNA which controls the cell.
observation	Evidence that is gotten directly through the senses.
open fracture	A fracture in which the ends of the bone go through the skin.
order	A division of classification larger than a family and smaller than a class.
organ	A group of tissues working together in the body. Example: stomach, brain, femur.
organism	Any single living thing.
organ system	A group of organs working together for one purpose in the body. Example: digestive system, skeletal system, nervous system.
over-the-counter drug	A drug which is able to be sold without a doctor's prescription
periosteum	The dense membrane ("skin") covering the outside of bones, except at the joints.
parasite	Any organism which lives on another living thing and harms it.
physical change	A change in matter, such as breaking, bending, or changing state, in which new molecules are not formed and the properties of the matter are not changed.
phylum	One of the large main groups contained within a kingdom (plural phyla).
pivot joint	A pivot joint allows movement turning from side to side. The head is attached to the vertebral column with this joint. A hole in one bone fits over a pointed part of the other bone, so that one bone can turn on top of the other.
pore	A small opening in the surface of an animal.
prescription drug	A drug which can only be sold by doctor's order.
property	A way of describing something. A trait of something. Properties of matter include such things as volume, mass, density, color, hardness, and reactivity.
proton	A subatomic particle found in the nucleus of the atom. It has a positive electric charge. The number of protons in an atom is called its atomic number. Each element has atoms of one atomic number.
reaction	A chemical change in which two or more substances form new substances. Examples of reactions include rusting, burning, and digesting.
re-entry	The return of a spacecraft into Earth's atmosphere.
reflex	A quick, automatic action which does not involve the brain.
satellite	An object which orbits another body in space. Our moon is a natural satellite. Sputnik was an artificial (man-made) satellite.
science	A way of learning knowledge which uses careful methods to test ideas and observations.
sensory nerve cell	A type of messenger nerve cell which gathers and sends information from the muscles to the brain or spinal cord.
shuttle	A vehicle which can go back and forth, making repeated trips.
side effect	An effect of a drug, usually unwanted, which is not intentional.
single-celled organism	An organism made of only one cell. It can live on its own and do everything all other living things can do, including reproduce.
skeletal muscle	Type of muscle which is attached to the bones of the skeleton and moves the skeleton. Skeletal muscle is voluntary muscle.
skeletal system	The bones of the skeleton.
sliding joint	A joint which allows small sliding movements. This joint is found between the vertebrae.
smooth muscle	A type of muscle which is found in the walls of organs. It is an involuntary muscle.
species	A group of related organisms which can interbreed.
spongy bone	In many torso bones and at the ends of the long bones, this light "honeycomb" bone is good at bearing stress. Otherwise known as "cancellous bone"
spore	A single cell which can grow into a new organism. Used by fungi and some plants for reproduction, instead of seeds.
sprain	A pull or tear in a ligament.
stinging cells	A special cell in Cnidarians called a cnidocyte. It contains a tiny harpoon-like structure, the nematocyst. When the cnidocyte is triggered, the nematocyst fires and delivers the toxin that stuns or kills the animal.
strain	A pull or tear in a muscle
stress fracture	A small crack in a bone, caused by working the bone too hard.
subatomic particle	The parts of an atom. They are tiny bits of energy. They include the neutron, the proton, and the electron. The neutron and proton are made of smaller subatomic particles called quarks.
suborbital	A space mission which goes less than one orbit. In other words, it does not circle the Earth, but goes up and comes back down.
substance	Something made of only one kind of matter. Each substance has its own properties which do not change.Substances are made up of only one kind of molecule or atom.
taxonomy	The science of classifying living things.
thorax	The middle part of an insect's body. The legs are attached to this part, and the wings if the animal has them.
tissue	A group of cells of similar type which work together. There are four main kinds in animals: epithelial, connective, muscle, and nervous tissues.
torso	The main trunk of the body, without the arms or legs.
tube foot	Echinoderms use these small tubes in order to move, by pumping water in and out of them.
vertebrae	The bones of the vertebral column.
volume	The size of something, in other words the amount of space something takes up.
voluntary muscle	A type of muscle which can be controlled by the conscious mind.
virus	A virus is a small molecule made of protein and genetic material. It can reproduce inside cells, but is not made of cells.
zoologist	A scientist who studies animals.