hardcover vs hardback

hardcover and hardback both are nouns.

Word	Noun	Adjective	Verb	Adverb
hardcover	Yes	Yes	No	No
hardback	Yes	Yes	No	No

As adjectives, hardcover and hardback are synonyms defined as:

Other synonyms of hardcover include hardbacked, hardbound.

As nouns, hardcover and hardback are synonyms defined as:

hardcover and hardback: a book with cardboard or cloth or leather covers

hardcover (noun)	hardback (noun)
a book with cardboard or cloth or leather covers	a book with cardboard or cloth or leather covers

hardcover (adjective)	hardback (adjective)
having a hard back or cover	having a hard back or cover