grommet vs fastener

grommet and fastener both are nouns.

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

As nouns, fastener is a hypernym of grommet; that is, fastener 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
fastener: restraint that attaches to something or holds something in place

Other hypernyms of grommet include fastening, fixing, holdfast.

grommet (noun)	fastener (noun)
fastener consisting of a metal ring for lining a small hole to permit the attachment of cords or lines	restraint that attaches to something or holds something in place
	a person who fastens or makes fast