Speculative fiction is a style of fiction which explores the nature of unproven entities or occurrences. In some contexts, it has been used as an inclusive term covering a group of fiction genres that speculate about worlds that are unlike the real world in various important ways. In these contexts, it generally includes science fiction, fantasy fiction, horror fiction, supernatural fiction, superhero fiction, alternate history, and magic realism. The term is used this way in academic and ideological criticism of these genres, as well as by some readers, writers, and editors of these genres.

Science fiction (abbreviated SF or sci-fi with varying punctuation and capitalization) is a broad genre of fiction that often involves speculations based on current or future science or technology. Science fiction is found in books, art, television, films, games, theatre, and other media. In organizational or marketing contexts, science fiction can be synonymous with the broader definition of speculative fiction, encompassing creative works incorporating imaginative elements not found in contemporary reality; this includes fantasy, horror, and related genres.

Science fiction differs from fantasy in that, within the context of the story, its imaginary elements are largely possible within scientifically established or scientifically postulated laws of nature (though some elements in a story...