Alternate history (also alternative history, allohistory, althist, AH) is a genre of speculative fiction of stories in which one or more historical events occur and are resolved differently than in real life. As conjecture based upon historical fact, alternate history stories propose What if? scenarios about crucial events in human history, and present outcomes very different from the historical record. Alternate history also is a subgenre of literary fiction, science fiction, and historical fiction; as literature, alternate history uses the tropes of the genre to answer the What if? speculations of the story. Since the 1950s, as a subgenre of science fiction, alternative history stories feature the tropes of time travel between histories, the psychic awareness of the existence of an alternative universe, by the inhabitants of a given universe; and time travel that divides history into various timestreams. In the Spanish, French, German, and Portuguese, Italian, Catalan, and Galician languages, the terms , , and identify the alternate history genre, from which derives the English term uchronia, composed of the Greek prefix ("not", "not any", and "no") and the Greek word () "time", to describe a story that occurs "[in] no time"; analogous to a story that occurs in utopia, "[in] no place". The term uchronia also is the name of the list of alternate-history books, Uchronia: The Alternate History List. Definition Often described as a subgenre of science fiction, Alternative History is a genre of fiction wherein the author speculates upon how the course of history might have been altered if a particular historical event had an outcome different from the real life outcome. An alternate history requires three conditions: (i) A point of divergence from the historical record, before the time in which the author is writing; (ii) A change that would alter known history; and (iii) An examination of the ramifications of that alteration to history. Occasionally, some types of genre fiction are misidentified as alternative history, specifically science fiction stories set in a time that was the future for the writer, but now is the past for the reader, such as the novels 2001: A Space Odyssey (1968), by Arthur C. Clarke and Nineteen Eighty-Four (1949), by George Orwell, because the authors did not alter the history of the past when they wrote the stories. Some alternative history stories feature the tropes of time travel between histories, and the psychic awareness of the existence of