postscript

An addendum to a letter, added after the author's signature.

As a rule Julian dictated to secretaries, and so fast that Libanius says the "tachygraphers" were unable to keep pace with him, but certain postscripts are marked "with his own hand."

An addition to a story, play, etc. after its completion.

In a moving post-script to the novel, Forster tells the reader that the book was inspired by a visit to the home of Edward Carpenter.

And then a curious postscript: I share your dislike of the shortening of names but I must say that I'm not sure 'Alexandra' is entirely suitable for you. It seems to me that you require a name with rather more brio. I see you as a 'Lexie'. What do you think?

To extend (a letter or another document) with additional remarks.