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if and only if.


Identification, Friend or Foe: a system of transmitters and transponders that uses coded signals to distinguish between friendly and hostile aircraft. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for iff
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Historical Examples
  • iff grinned and hung his head as if embarrassed, rubbing a handkerchief over the smoke-stained fingers of his right hand.

    The Bandbox Louis Joseph Vance
  • But that same reseit, iff your Honner so please, to cure a shrewish wife.

    Clarissa, Volume 3 (of 9) Samuel Richardson
  • Mr. iff routed a negligible quibble with an airy flirt of his delicate hand.

    The Bandbox Louis Joseph Vance
  • And what wold ye doe with my bryde soe gay, iff I did sell her thee?

  • Diving into a bathrobe, he turned the water on for his bath, trotted to the front room and discovered the evasion of Mr. iff.

    The Bandbox Louis Joseph Vance
  • Mr. iff enquired in simple surprise: “Do you really care to know?”

    The Bandbox Louis Joseph Vance
  • Round it were grouped in various attitudes of dejection sundry other pieces of travelling-gear and Mr. iff.

    The Bandbox Louis Joseph Vance
  • It was, in fact, the bandbox which had first fixed the interest of Mr. iff.

    The Bandbox Louis Joseph Vance
  • iff raised himself on his elbow to stare at Staff as if questioning his sanity.

    The Bandbox Louis Joseph Vance
British Dictionary definitions for iff


(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


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
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iff in Technology

1. Interchange File Format.
2. Identify friend or foe (radar).

mathematics, logic
if and only if, i.e. necessary and sufficient. For example, two figures are congruent iff one can be placed over the other so that they coincide.

The Free On-line Dictionary of Computing, © Denis Howe 2010
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Related Abbreviations for iff


if and only if


identification, friend or foe
The American Heritage® Abbreviations Dictionary, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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