What is the difference between an autobiography, a diary, and memoirs?

Question

All are written by a person about themselves, why do we need 3 different words?

In: 1

Answer 1

A diary is just a book that someone writes for themselves and usually not something written with the intent of publication (even if it does get published later).

A memoir is a subcategory of autobiography. An autobiography is the story of their life, a memoir is when it only covers specific time periods or certain events. For example a book that only covers childhood and makes no mention of their adult years would probably be considered a memoir.

They’re used fairly interchangeable because defining an exact boundary for when it covers too much to be considered a memoir isn’t really useful to anyone.