iff

¹ American  

Mathematics.

1. if and only if.

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IFF ² American  

Military.

1. Identification, Friend or Foe: a system of transmitters and transponders that uses coded signals to distinguish between friendly and hostile aircraft.

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IFF ¹ British  

abbreviation

1. Identification, Friend or Foe: a system using radar transmissions to which equipment carried by friendly forces automatically responds with a precoded signal

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iff ² British  

/ ɪf /

conjunction

1. logic a shortened form of if and only if : it indicates that the two sentences so connected are necessary and sufficient conditions for one another. Usually iff is used for equivalence in the metalanguage, rather than as the biconditional in the object language

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Example Sentences

The Ministerium's pleasure in learning that its income had risen for the first time in six years was tempered by the realization that the rise amounted to iff per week per member.

From Time Magazine Archive

Another who believed in Scurry's future was Edith McKanna, a handsome, fortyish widow, who began buying up leases iff 1945 when she got out of the armed services.

From Time Magazine Archive

Formed iff 1925 by an expatriated Viennese musician named Alexander Lippay, the Manila Symphony at first had hard sledding, often played to audiences of fewer than 100 people.

From Time Magazine Archive

If the latter, you are making a grave mistake for you are sure iff lose subscribers by so doing.

From Time Magazine Archive

He was sher- iff so long that we growing up in Monterey County thought the words “Sheriff” and “Quinn” went together naturally.

From "East of Eden" by John Steinbeck