Definition of "iff" []

• If and only if (abbreviation)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "This may get a little confusing but the difference for the sake of argument between 'if' and 'iff' is as follows:"
• "˜Snow is white™ is true in English iff snow is white."
• "By the way, the use of 'iff' in the introduction is not a typo, it's a shorthand used by philosophers for if and only if."