remnant vs piece of material

remnant and piece of material both are nouns.

Word	Noun	Adjective	Verb	Adverb
remnant	Yes	No	No	No
piece of material	Yes	No	No	No

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

remnant: a piece of cloth that is left over after the rest has been used or sold
piece of material: a separate part consisting of fabric

Other hypernyms of remnant include piece of cloth.

remnant (noun)	piece of material (noun)
a piece of cloth that is left over after the rest has been used or sold	a separate part consisting of fabric
a small part or portion that remains after the main part no longer exists