noun

1. a statement universally accepted as true; maxim
2. an established principle or law of a science, art, etc.
3. Logic, Math. a statement or proposition that needs no proof because its truth is obvious, or one that is accepted as true without proof Euclid's axiom that things equal to the same thing are equal to each other

Etymology: Fr axiome < L axioma < Gr axiōma, authority, authoritative sentence < axioun, to think worthy < axios, worthy < base of agein, to weigh, orig., to lend: see act