1. [noun] (philosophy) A seemingly self-evident or necessary truth which is based on assumption; a principle or proposition which cannot actually be proved or disproved.
2. [noun] (mathematics) (logic) (proof theory) A fundamental assumption that serves as a basis for deduction of theorems. Examples: 'Through a pair of distinct points there passes exactly one straight line', 'All right angles are congruent'.
3. [noun] An established principle in some artistic practice or science that is universally received.
4. [noun] A saying that is widely accepted on its own merits.
5. [noun] (logic) a proposition that is not susceptible of proof or disproof; its truth is assumed to be self-evident.
