Definition of iff in English:

iff

conjunction ɪfif

Mathematics Logic

If and only if.
〔逻，数〕在…而且只有在…的条件下
Example sentencesExamples
- 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.
- The truth conditions for negation are: A is true iff A is not true.
- 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.
- 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).
- Thus the sentence ‘Snow is white’ is true iff it corresponds to the fact that snow is white.

Origin

1950s: arbitrary extension of if.

Definition of iff in US English:

iff

conjunctionif

Logic Mathematics

If and only if.
〔逻，数〕在…而且只有在…的条件下
Example sentencesExamples
- Thus the sentence ‘Snow is white’ is true iff it corresponds to the fact that snow is white.
- 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.
- 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.
- 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).
- The truth conditions for negation are: A is true iff A is not true.

Origin

1950s: arbitrary extension of if.

单词	iff
释义	Definition of iff in English: iff conjunction ɪfif Mathematics Logic If and only if. 〔逻，数〕在…而且只有在…的条件下 Example sentencesExamples 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. The truth conditions for negation are: A is true iff A is not true. 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. 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). Thus the sentence ‘Snow is white’ is true iff it corresponds to the fact that snow is white. Origin 1950s: arbitrary extension of if. Definition of iff in US English: iff conjunctionif Logic Mathematics If and only if. 〔逻，数〕在…而且只有在…的条件下 Example sentencesExamples Thus the sentence ‘Snow is white’ is true iff it corresponds to the fact that snow is white. 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. 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. 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). The truth conditions for negation are: A is true iff A is not true. Origin 1950s: arbitrary extension of if.
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