dust cover vs piece of material

dust cover and piece of material both are nouns.

Word	Noun	Adjective	Verb	Adverb
dust cover	Yes	No	No	No
piece of material	Yes	No	No	No

As nouns, piece of material is a hypernym of dust cover; that is, piece of material is a word with a broader meaning than dust cover:

dust cover: a large piece of cloth used to cover furniture that is not in use for a long period
piece of material: a separate part consisting of fabric

Other hypernyms of dust cover include piece of cloth.

dust cover (noun)	piece of material (noun)
a removable plastic protective covering for a piece of equipment	a separate part consisting of fabric
a large piece of cloth used to cover furniture that is not in use for a long period
a paper jacket for a book; a jacket on which promotional information is usually printed