Sci-fi is an abbreviation for science fiction. It was coined in 1954 by Forrest J. Ackerman as a pun on the term "hi-fi". Many science fiction fans initially reacted negatively to the word.

Another abbreviation for science fiction is "SF". However, "sci-fi" is more common in popular usage outside science fiction fandom. Despite this almost universal acceptance of the word, many science fiction fans still cringe when they hear it.

Sometimes the word is used to mean particularly poor or campy examples of science fiction. For example, under such usage, Plan 9 from Outer Space might be considered sci-fi. In this usage it is often spelled "skiffy" which is pronounced to rhyme with "jiffy".

Another source of dislike for the sci-fi term is the tendency for the mainstream to use it as a collective term that lumps together not only true science fiction but fantasy, horror, comic books, cult films, special effects action films, only marginally related genres such as anime and gaming, and completely unrelated fields such as UFOlogy.

Despite this controversy, two high-profile science fiction-based cable networks in the United States and Great Britain take their name from this term, although both networks air programming which may not fit into everyone's definition of "science fiction."

A variation of the term is "sci-fantasy".

See also: Speculative fiction

The name "Sci Fi" also is used by:

• a British satellite television channel; see Sci Fi Channel (United Kingdom)
• a United States television channel; see Sci Fi Channel (United States)