iff

conjunction \ ˈif-ᵊn(d)-ˈōn-lē-ˌif ; ˈif , sometimes read with a prolonged f \

Definition of iff

:if and only if
  • two figures are congruent iff one can be placed over the other so that they coincide
used in logic and mathematics

Origin and Etymology of iff

alteration of 1if


IFF

abbreviation

Definition of IFF

identification, friend or foe

Learn More about iff


Seen and Heard

What made you want to look up iff? Please tell us where you read or heard it (including the quote, if possible).

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

WORD OF THE DAY

pleasing or sweet sound

Get Word of the Day daily email!

Test Your Vocabulary

Forms of Government Quiz

  • knupfer-painting-solon-before-croesus
  • A gerontocracy is rule by:
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

TAKE THE QUIZ
SCRABBLE® Sprint

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!