soft-cover book vs paperback

soft-cover book and paperback both are nouns.

Word	Noun	Adjective	Verb	Adverb
soft-cover book	Yes	No	No	No
paperback	Yes	Yes	No	No

As nouns, soft-cover book and paperback are synonyms defined as:

Other synonyms of soft-cover book include paper-back book, paperback book, soft-cover, softback, softback book.

soft-cover book (noun)	paperback (noun)
a book with paper covers	a book with paper covers

soft-cover book (adjective)	paperback (adjective)
	(of books) having a flexible binding