n. 1 (context uncountable English) A class of fiction including but not necessarily limited to fantasy, horror(,) and science fiction, dealing with worlds, themes(,) and characters not part of everyday life. 2 (context countable English) A particular work belonging to this class.
Speculative fiction is a broad category of narrative fiction that includes elements, settings and characters created out of imagination and speculation rather than based on reality and everyday life. It encompasses the genres of science fiction, fantasy, science fantasy, horror, alternative history, and magic realism. It typically strays strongly from reality and so may feature fictional types of beings like mythical creatures and supernatural entities, technologies that do not exist in real life like time machines and interstellar spaceships, or magical or otherwise scientifically inexplicable elements. The term's popularity is sometimes attributed to Robert Heinlein, who referenced it in 1947 in an editorial essay, although there are prior mentions of speculative fiction, or its variant "speculative literature".