volume vs paperback

volume and paperback both are nouns.

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

As nouns, paperback is a hyponym of volume; that is, paperback is a word with a more specific, narrower meaning than volume:

volume (noun)	paperback (noun)
physical objects consisting of a number of pages bound together	a book with paper covers
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

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