# Primitive notion

In

mathematics, a

**primitive notion** is something that is not defined in terms of previously defined terms. That is, it is something that is taken to be true as an

axiom rather than something that can be proved from a set of further axioms. For example in

naive set theory, the notion of the existence of the

empty set is primitive. For a more formal discussion of the foundations of mathematics see the

axiomatic set theory article.