soft-cover vs softback

soft-cover and softback both are nouns.

Word	Noun	Adjective	Verb	Adverb
soft-cover	Yes	No	No	No
softback	Yes	No	No	No

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

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

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