grommet vs fastening

grommet and fastening both are nouns.

Word	Noun	Adjective	Verb	Adverb
grommet	Yes	No	No	No
fastening	Yes	No	No	No

As nouns, fastening is a hypernym of grommet; that is, fastening is a word with a broader meaning than grommet:

grommet: fastener consisting of a metal ring for lining a small hole to permit the attachment of cords or lines
fastening: restraint that attaches to something or holds something in place

Other hypernyms of grommet include fastener, fixing, holdfast.

grommet (noun)	fastening (noun)
fastener consisting of a metal ring for lining a small hole to permit the attachment of cords or lines	the act of fastening things together
	restraint that attaches to something or holds something in place