postscript vs supplement

postscript

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

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

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

supplement

noun
  • An extension to a document or publication that adds information, corrects errors or brings up to date. 

  • A vitamin, herbal extract or chemical compound ingested to meet dietary deficiencies or enhance muscular development. 

  • Something added, especially to make up for a deficiency. 

  • An additional section of a newspaper devoted to a specific subject. 

  • An angle that, when added to a given angle, makes 180°; a supplementary angle. 

  • A surcharge, additional cost, especially for food in a restaurant. 

verb
  • To provide or make a supplement to something. 

How often have the words postscript and supplement occurred in a corpus of books? (source: Google Ngram Viewer )