Definition of iff in English:

iff

Line breaks: iff

conjunction

Logic & Mathematics
  • If and only if.
    More example sentences
    • Let the letter ‘M’ represent this operator, and add to the axioms of classical propositional logic the modal axiom M (p v q) iff Mp v Mq.
    • The truth conditions for negation are: A is true iff A is not true.
    • Let us say that I could have rendered a proposition false in the weak sense iff I was able to do something such that, if I did it, the proposition would have been falsified (though not necessarily by my act, or by any event caused by my act).

Origin

1950s: arbitrary extension of if.

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