/ ˌæksiəˈmætɪk; NAmE / adjective
[ not usually before noun ] ( formal ) true in such an obvious way that you do not need to prove it
SYN self-evident :
It is axiomatic that life is not always easy.
► axio·mat·ic·al·ly adverb
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WORD ORIGIN
late 18th cent.: from Greek axiōmatikos , from axiōma what is thought fitting, from axios worthy.