axiom axiom /ˈæksiːəm/

noun

1. () A saying that is widely accepted on its own merits  ( axiom , maxim )
   a saying that is widely accepted on its own merits
   
2. (logic) a proposition that is not susceptible of proof or disproof; its truth is assumed to be self-evident  ( axiom )
   (logic) a proposition that is not susceptible of proof or disproof; its truth is assumed to be self-evident