/
ˈaksɪəm/
n.
  - an accepted statement or proposition regarded as being self-evidently true.
 - chiefly Mathematics  a statement or proposition on which an abstractly defined structure is based.
 
Derivative
- axiomatic adj.
  - axiomatically adv.
 
Etymology
C15: from Fr. axiome or L. axioma, from Gk axiōma, from axios ‘worthy’.