An autobiography (from the Greek, αὐτός-autos self + βίος-bios life + γράφειν-graphein to write) is a book about the life of a person, self-authored by that person.
All fiction may be autobiography, but all autobiography is of course fiction.
Shirley Abbott, quoted in Mickey Pearlman, Listen to Their Voices (1993), ch. 12.
Every autobiography is concerned with two characters, a Don Quixote, the Ego, and a Sancho Panza, the Self.
W. H. Auden, The Dyer’s Hand (1962), pt. 3, “Hic et Ille”, sect. b
Reminiscences, even extensive ones, do not always amount to an autobiography. For even if months and years appear here, it is in the form they have in the moment of recollection. This strange form—it may be called fleeting or eternal—is in neither case the stuff that life is made of.
Devil walks into bar. Orders drink. Asks Philosopher sitting next to him: “And what do you do?”