A Proposition regarded as self-evidently True without Proof. The word ``axiom'' is a slightly archaic synonym for Postulate. Compare Conjecture or Hypothesis, both of which connote apparently True but not self-evident statements.
See also Archimedes' Axiom, Axiom of Choice, Axiomatic System, Cantor-Dedekind Axiom, Congruence Axioms, Conjecture, Continuity Axioms, Countable Additivity Probability Axiom, Dedekind's Axiom, Dimension Axiom, Eilenberg-Steenrod Axioms, Euclid's Axioms, Excision Axiom, Fano's Axiom, Field Axioms, Hausdorff Axioms, Hilbert's Axioms, Homotopy Axiom, Inaccessible Cardinals Axiom, Incidence Axioms, Independence Axiom, Induction Axiom, Law, Lemma, Long Exact Sequence of a Pair Axiom, Ordering Axioms, Parallel Axiom, Pasch's Axiom, Peano's Axioms, Playfair's Axiom, Porism, Postulate, Probability Axioms, Proclus' Axiom, Rule, T2-Separation Axiom, Theorem, Zermelo's Axiom of Choice, Zermelo-Fraenkel Axioms