art collection vs collection

art collection and collection both are nouns.

Word	Noun	Adjective	Verb	Adverb
art collection	Yes	No	No	No
collection	Yes	No	No	No

As nouns, collection is a hypernym of art collection; that is, collection is a word with a broader meaning than art collection:

Other hypernyms of art collection include accumulation, aggregation, assemblage.

art collection (noun)	collection (noun)
a collection of art works	the act of gathering something together
	a publication containing a variety of works
	request for a sum of money
	several things grouped together or considered as a whole