paperback vs volume

paperback and volume both are nouns.

Word	Noun	Adjective	Verb	Adverb
paperback	Yes	Yes	No	No
volume	Yes	No	No	No

As nouns, volume is a hypernym of paperback; that is, volume is a word with a broader meaning than paperback:

Other hypernyms of paperback include book.

paperback (noun)	volume (noun)
a book with paper covers	physical objects consisting of a number of pages bound together
	the magnitude of sound (usually in a specified direction)
	the property of something that is great in magnitude
	a publication that is one of a set of several similar publications
	the amount of 3-dimensional space occupied by an object
	a relative amount

paperback (adjective)	volume (adjective)
(of books) having a flexible binding