iff

Mathematics.

if and only if.

IFF

Military.

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

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for iff

Contemporary Examples of iff

The IFF, however, is not exactly an organization to be proud of.
The Real Jersey Dictionary, Vol. 2
Jaimie Etkin
October 21, 2010

Historical Examples of iff

I could like her better, iff she was better to my young lady.
Clarissa, Volume 3 (of 9)
Samuel Richardson
But that same reseit, iff your Honner so please, to cure a shrewish wife.
Clarissa, Volume 3 (of 9)
Samuel Richardson
And what wold ye doe with my bryde soe gay, Iff I did sell her thee?
A Book of Ballads, Volume 1
Various
Mr. Iff enquired in simple surprise: “Do you really care to know?”
The Bandbox
Louis Joseph Vance
Mr. Staff, I want you to shake hands with my friend, Mr. Iff.
The Bandbox
Louis Joseph Vance

British Dictionary definitions for iff

iff

conjunction

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

IFF

abbreviation for

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

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012