- (music) The solfeggio syllable used to indicate the sharp of the fourth note of a major scale.
- (in combination) Abbreviation of fidelity. (e.g. in hi-fi or wi-fi)
- (in combination) Abbreviation of fiction. (e.g. in sci-fi)
The word if spelled backwards, introduced in the ALGOL 68 Report (1968) as a terminator for an if clause.
- (computer science) Reserved word, in some programming languagess, signaling the end of an "if" program instruction.