I wondered if I'd goofed and used the word memoir on my own. So I checked the book on Amazon, and the title is Known and Unknown and underneath that it says A Memoir. I breathed a sigh of relief because I don't like to make mistakes and I especially don't like to make them publicly.
I kept thinking about it, however, so this morning I went to Webster to define memoir and autobiography. The dictionary gave me this for memoir:
Definition of MEMOIR
: an official note or report : memorandum
a : an account of something noteworthy : reportb plural : the record of the proceedings of a learned society
and the definition of autobiography is:
au·to·bi·og·ra·phynoun \ˌȯ-tə-bī-ˈä-grə-fē, -bē-\
: the biography of a person narrated by himself or herself
So it looks like an autobiography can also be termed a memoir. If you adhere to dictionary definitions, they might be used interchangeably. My personal feeling is that an autobiography is the complete story of a life. A memoir can be the same, or it can be just one slice of the pie.