Postscript

A postscript may be a sentence, a paragraph, or occasionally many paragraphs added, often hastily and incidentally, after the signature of a letter or the main body of an essay or book. For such longer works it may also be known as an afterword or subscription. The term comes from the Latin "post scriptum", an expression meaning "written after".

Afterword

In a book or essay, a more carefully composed addition is called an afterword. It is a literary device that is often found at the end of a piece of literature. It generally covers the story of how the book came into being, or of how the idea for the book was developed.
An afterword may be written by someone other than the author of the book to provide enriching comment, such as discussing the work's historical or cultural context.

Addendum

The word "postscript" has poetically been used to refer to any sort of addendum to some main work even if it is not attached to a main work, for example Søren Kierkegaard's book titled Concluding [Unscientific Postscript]. Such a section may also be called a "subscription", for example a subscription is found at the end of St Paul's Paul's Second [Letter to the Corinthians|Second Letter to the Corinthians] in some Biblical manuscript#New [Testament manuscripts|manuscripts], stating that it was written by Paul when he was at Philippi, a city of Macedonia, and transcribed by Titus and Lucas.

Cascading postscripts

Sometimes when additional points are made after the first postscript, abbreviations such as P.P.S. and P.P.P.S. and so on are added, ad infinitum.