append vs supplement

append is not a noun while supplement is a noun.

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

As verbs, append and supplement are synonyms defined as:

Other synonyms of append include add on, affix.

append (noun)	supplement (noun)
	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

append (verb)	supplement (verb)
state or say further	add to the very end
fix to; attach	add as a supplement to what seems insufficient
add to the very end	serve as a supplement to