Cally Ang: What Does P.S Means ?

P.S. at the end of letter is abbreviated for

: Postscript, a message at the end of a letter or other piece of writing. "Post-" = after; "script" = writing.

Post Scriptum in the ancient Roman tongue, which is why it's two letters, even though our English word postscript has become one word.

Sources:

http://www.phrases.org.uk/bulletin_board/17/messages/728.html