Science fiction is a genre of speculative fiction, which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel universes, and extraterrestrial life. It is related to fantasy, horror, and superhero fiction and contains many subgenres. Its exact definition has long been disputed among authors, critics, scholars, and readers.

Speculative fiction is an umbrella genre of fiction that encompasses all the subgenres that depart from realism, or strictly imitating everyday reality, instead presenting fantastical, supernatural, futuristic, or other imaginative realms. This catch-all genre includes, but is not limited to, science fiction, fantasy, horror, slipstream, magical realism, superhero fiction, alternate history, utopia and dystopia, fairy tales, steampunk, cyberpunk, weird fiction, and some apocalyptic and post-apocalyptic fiction. The term has been used for works of literature, film, television, drama, video games, radio, and their hybrids.