Definition from Wiktionary, the free dictionary
postscript (plural postscripts)
- (countable) An addendum to a letter, added after the author’s signature.
- (countable) An addition to a story, play, etc.
In a letter, to indicate the beginning of a postscript one often uses the abbreviation P.S. followed by a colon.
addendum to a letter
- To extend (a letter etc.) with additional remarks.