Postscript

(n.) An addition 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.

Thesaurus Entries

PS, Parthian shot, addendum, affix, afterthought, allonge, appendix, back matter, chorus, coda, codicil, colophon, commentary, conclusion, consequence, continuance, continuation, double take, dying words, enclitic, envoi, epilogue, follow-through, follow-up, infix, interlineation, interpolation, last words, marginalia, note, parting shot, peroration, postface, postfix, postlude, prefix, proclitic, refrain, rider, scholia, second thought, sequel, sequela, sequelae, sequelant, sequent, sequitur, subscript, suffix, supplement, swan song, tag, tail