Postscriptum vs. Postscript — What's the Difference?

(rare) A thing that has been written afterwards; something appended in writing.

A postscript (P.S.) is an afterthought, thought that is occurring after the letter has been written and signed. The term comes from the Latin post scriptum, an expression meaning "written after" (which may be interpreted in the sense of "that which comes after the writing").A postscript may be a sentence, a paragraph, or occasionally many paragraphs added, often hastily and incidentally, after the signature of a letter or (sometimes) the main body of an essay or book.

A message appended at the end of a letter after the writer's signature.

Additional information appended to the manuscript, as of a book or article.

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

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

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

A paragraph added to a letter after it is concluded and signed by the writer; an addition made to a book or composition after the main body of the work has been finished, containing something omitted, or something new occurring to the writer.

A note appended to a letter after the signature

Textual matter that is added onto a publication; usually at the end