Emily Dickinson Lexicon

AX'IOM, n. [Gr. αξιωμα, authority, an authoritative sentence, or that which is assumed, from αξιος, worthy, αξιοω, to think worthy, to esteem; Eng. to ask (to ax;) that which is asked, sought or esteemed.]

1. A self-evident truth, or a proposition whose truth is so evident at first sight, that no process of reasoning or demonstration can make it plainer; as, “the whole is greater than a part.” – Johnson. Encyc.
2. An established principle in some art or science, a principle received without new proof; as, “things which are equal to the same thing, are equal to one another.” Encyc.