piece of material vs fabric

piece of material and fabric both are nouns.

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

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

piece of material: a separate part consisting of fabric
fabric: artifact made by weaving or felting or knitting or crocheting natural or synthetic fibers

Other hypernyms of piece of material include cloth, material, textile, piece.

piece of material (noun)	fabric (noun)
a separate part consisting of fabric	artifact made by weaving or felting or knitting or crocheting natural or synthetic fibers
	the underlying structure