What term describes anything that occupies space and possesses mass?

The term that describes anything that occupies space and possesses mass is "matter." Matter is the foundational concept in physics and chemistry, encompassing all physical substances. This includes everything from the air we breathe to the water we drink, as well as solid objects like wood or metal. Matter can exist in different states—solid, liquid, gas, or plasma—each occupying space and exhibiting mass, which is a measure of how much matter is contained within an object.

In contrast, other terms like element, compound, and particle have more specific definitions. An element refers to a pure substance that cannot be broken down into simpler substances by chemical means, such as hydrogen or oxygen. A compound is a substance formed when two or more elements chemically bond together, like water (H2O) or carbon dioxide (CO2). A particle generally refers to a small localized object, which can be a fundamental constituent of matter like atoms or molecules, but does not encompass the broader definition of matter itself. Therefore, matter is the most comprehensive term that includes all substances that have mass and take up space.