sequel vs postscript

sequel and postscript both are nouns.

Word	Noun	Adjective	Verb	Adverb
sequel	Yes	No	No	No
postscript	Yes	No	No	No

As nouns, postscript is a hypernym of sequel; that is, postscript is a word with a broader meaning than sequel:

sequel: a part added to a book or play that continues and extends it
postscript: textual matter that is added onto a publication; usually at the end

Other hypernyms of sequel include addendum, supplement.

sequel (noun)	postscript (noun)
a part added to a book or play that continues and extends it	a note appended to a letter after the signature
something that follows something else	textual matter that is added onto a publication; usually at the end