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READ THESE ARTICLES# Definition of *iff* in English:

## iff

### conjunction

Logic MathematicsIf and only if (as a written abbreviation).

*‘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).’**‘Minimalism allows us to generate a minimal truth condition for any meaningful indicative sentence, such as ‘Lying is wrong’ is true iff lying is wrong.’**‘Thus the sentence ‘Snow is white’ is true iff it corresponds to the fact that snow is white.’*

**Origin**

1950s arbitrary extension of if.

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