The word substance comes from the Latin word substantia, which literally means “to stand under.”
(1) The physical matter, material, or substance that makes up an organ or a body.
(2) (In chemistry) A substance, matter, or object with a particular chemical composition and quality.
(3) The most important or necessary component of something.
(4) Substance misuse, as in drugs.
The term substance is used in biology to refer to the material that makes up an organ, such as ground substance or spongy substance. All compounds are substances in chemistry, but not all substances are compounds, because pure elements are chemical substances as well.
Chemical compounds can take the form of a solid, a liquid, or a gas. Water, salt, sugar, and other substances are examples. Light and heat are examples of energy that is not considered chemical substances.