axiom

noun

ax·​i·​om ˈak-sē-əm 

1

: a statement accepted as true as the basis for argument or inference : postulate sense 1

one of the axioms of the theory of evolution

2

: an established rule or principle or a self-evident truth

cites the axiom "no one gives what he does not have"

3

: a maxim widely accepted on its intrinsic merit

the axioms of wisdom

Did you know?

In mathematics or logic, an axiom is an unprovable rule or first principle accepted as true because it is self-evident or particularly useful. “Nothing can both be and not be at the same time and in the same respect” is an example of an axiom. The term is often used interchangeably with postulate, though the latter term is sometimes reserved for mathematical applications (such as the postulates of Euclidean geometry). It should be contrasted with a theorem, which requires a rigorous proof.

Examples of axiom in a Sentence

one of the key axioms of the theory of evolution

Recent Examples on the Web

These shows were built around heady concepts like a sequence, an axiom or the work of Pablo Picasso. —Heather Bushman, IndyStar, 17 Nov. 2025

His preference would be to find simpler axioms for quantum mechanics — intuitive principles that would let theorists re-derive the theory in a new form altogether. —Daniel Garisto, Quanta Magazine, 7 Nov. 2025

Read More: Why Trump Didn't Deserve the Nobel Peace Prize The Russian President is a man who lives by the axiom: give an inch, take a mile. —Luke McGee, Time, 21 Oct. 2025

In other words, as Cleveland tore through the league last season, the players responded to most of the milestones reached with a collective shrug and worn axioms about nothing mattering until the playoffs. —Joe Vardon, New York Times, 2 Oct. 2025

Word History

Etymology

borrowed from Middle French & Latin; Middle French axiome, borrowed from Latin axiōma "fundamental proposition," borrowed from Greek axíōma "honor, honored status, prestige, that which is reasonable (though not demonstrated to be true), self-evident principle," from axiō-, variant stem of axióō, axioûn "to consider worthy, value, consider appropriate, claim, think" (verbal derivative of áxios "valued [at a sum of money], worth, equal, of an equivalent status, worthy, suitable," of uncertain origin) + -ma, resultative noun suffix

Note: The Greek adjective áxios has conventionally been taken as originally meaning "of equal weight, counterbalancing"—hence it is seen as a derivative of an unattested noun *axis "weight" (< *ag-ti-), a derivative of ágein "to lead, carry off," also, among many other senses, "to weigh (a certain amount)," though the latter meaning is no earlier than fifth-century Attic.

First Known Use

15th century, in the meaning defined at sense 3

Phrases Containing axiom

• axiom of choice

Kids Definition

axiom

noun

ax·​i·​om ˈak-sē-əm 

: a rule or principle widely accepted as obviously true and not needing to be proved