Preface? Forward? Difference???

Looking for help from the Doper Literati.

Preceding the body of a book, what are the definitions of “preface” and “foreward”?

Sometimes they seem interchangeable.

pref·ace (prfs)
n. Abbr. pref.
A preliminary statement or essay introducing a book that explains its scope, intention, or background and is **usually written by the author. **
An introductory section, as of a speech.
Something introductory; a preliminary: An informal brunch served as a preface to the three-day conference.
Often Preface. The words introducing the central part of the Eucharist in several Christian churches.
fore·word (fôrwrd, fr-)
n.

A preface or an introductory note, as for a book, especially by a person other than the author.

Both the preface and the foreword are introductory remarks. These introductory remarks tend to be called foreword when they are by someone other than the author of the main work, and either foreword or preface when they are by the main work’s author.

Thanks.

Definitions are one thing, but often actual practice tends to deviate from definitions - and it always takes formal definitions a while to catch up to reality.

When written by the author, is there any convention for selecting one term over the other, or does it depend on the author or editor?

This reminds me of a funny book by Stanislav Lem, its a collection of the prefaces of imaginary books. I think the books title was “A Perfect Vaccuum” but I’m not sure.

Anyway, the book starts out with a preface of its own, containing a wonderful self-referrential statement:

Preface:

I have always thought the art of writing prefaces deserved more attention.