Axiom

An axiom is a law or rule, usually self-evident, that is used in math and logic. One common example of a mathematical axiom is the Pythagorean Theorem that we all learned in math class about finding the unknown side of a 3-sided figure (A squared X B squared = c squared). In a logical sense an an example of an axiom is "All things on the earth are affected by gravity. A self-evident truth.