paste-up vs collage

paste-up and collage both are nouns.

Word	Noun	Adjective	Verb	Adverb
paste-up	Yes	No	No	No
collage	Yes	No	No	No

As nouns, collage is a hyponym of paste-up; that is, collage is a word with a more specific, narrower meaning than paste-up:

paste-up: a composition of flat objects pasted on a board or other backing
collage: a paste-up made by sticking together pieces of paper or photographs to form an artistic image

Other hyponyms of paste-up include montage.

paste-up (noun)	collage (noun)
a composition of flat objects pasted on a board or other backing	a paste-up made by sticking together pieces of paper or photographs to form an artistic image
	any collection of diverse things