An autobiography is a book about the life of a person, written by that person. The form of autobiography goes back to antiquity. Biographers generally rely on a wide variety of documents and viewpoints; an autobiography, however, may be based entirely on the writer's memory. Closely associated with autobiography (and sometimes difficult to precisely distinguish from it) is the form of memoir.
A memoir forms a subclass of autobiography – although the terms 'memoir' and 'autobiography' are almost interchangeable in modern parlance. Memoir is autobiographical writing, but not all autobiographical writing follows the criteria for memoir.