Memoir or Autobiography, which is correct?

A memoir (singular) is traditionally considered to be an intimate account of a personal event. A collection of memoirs can be similar to an autobiography, but memoirs may center around a single theme (such as James Herriot's "All Creatures Great and Small," about his work as a small-town vet), rather than standing as a straightforward account of a person's life. They are often used interchangeably in publishing today.