addendum vs supplement

addendum and supplement both are nouns.

Word	Noun	Adjective	Verb	Adverb
addendum	Yes	No	No	No
supplement	Yes	No	Yes	No

As nouns, addendum and supplement are synonyms defined as:

addendum and supplement: textual matter that is added onto a publication; usually at the end

Other synonyms of addendum include postscript.

addendum (noun)	supplement (noun)
textual matter that is added onto a publication; usually at the end	a supplementary component that improves capability
	a quantity added (e.g. to make up for a deficiency)
	textual matter that is added onto a publication; usually at the end

addendum (verb)	supplement (verb)
	add to the very end
	add as a supplement to what seems insufficient
	serve as a supplement to