An axiom or postulate as defined in classic philosophy, is a statement (in mathematics often shown in symbolic form) that is so evident or well-established, that it is accepted without controversy or question. Thus, the axiom can be used as the premise or starting point for further reasoning or arguments, usually in logic or in mathematics The word comes from the Greek axíoma 'that which is thought worthy or fit' or 'that which commends itself as evident.'

An axiom is a proposition in mathematics and epistemology that is taken to be self-evident.