Alternative History

Alternate history or alternative history is a subgenre of speculative fiction (or science fiction) and historical fiction that is set in a world in which history has diverged from the actual history of the world. It is sometimes abbreviated AH. Another occasionally-used term for the genre is "allohistory" Since the 1950s, this type of fiction has to a large extent merged with science fictional tropes involving cross-time travel between alternate histories or psychic awareness of the existence of "our" universe by the people in another; or ordinary voyaging uptime or downtime that results in history splitting into two or more timelines. Cross-time, time-splitting and alternate history themes have become so closely interwoven that it is impossible to discuss them fully apart from one another.