Roanne Butier recently brought this questioni to my attention:
“The Scrabble dictionary contains the “word” iff. They say it’s a conjunction meaning “if and only if”. That makes no sense to me. If you speak a sentence using iff, no one could tell if you mean if or iff. You could only use it in writing. I can’t believe it’s really a word. Your comments please.”
Only mathematicians and the philosophers of logic use iff. It is not a word but an abbreviation of the phrase you quoted used only in formal logic: if and only if. As you can see, it comprises the first two letters and the final letter of the phrase.
Iff should be allowed as a Scrabble word only to the extent abbreviations are allowed. I don’t think they are. Words have pronunciations and this one doesn’t in the sense that no one pronounces it [if]; it is used only in writing. When logicians use it in speech, they always say, “if and only if”.