IFF


Meaning of IFF in English

transcription, транскрипция: [ ˈif- ə n(d)-ˈōn-lē-ˌif; ˈif, sometimes read with a prolonged ]

f conjunction

Etymology: alteration of if (I)

Date: 1955

: if and only if

two figures are congruent iff one can be placed over the other so that they coincide

Merriam-Webster's Collegiate English vocabulary.      Энциклопедический словарь английского языка Merriam Webster.