Fundamental

An object is fundamental if it is one of the elementary building blocks the universe is made of. (This definition is roughly synonymous with the one given by the Stanford Encyclopedia of Philosophy.) Conversely, non-fundamental objects are called composite or emergent.

Objects can also be placed on a spectrum based on how far removed from fundamental (i.e., how "high-level") they are. For example, an apple is a high-level composite object, a molecule is a low-level composite object, and an electron is a fundamental (and hence maximally low-level) object.