groomsman vs attender

groomsman and attender both are nouns.

Word	Noun	Adjective	Verb	Adverb
groomsman	Yes	No	No	No
attender	Yes	No	No	No

As nouns, attender is a hypernym of groomsman; that is, attender is a word with a broader meaning than groomsman:

groomsman: a male attendant of the bridegroom at a wedding
attender: someone who waits on or tends to or attends to the needs of another

Other hypernyms of groomsman include attendant, tender, adult male, man.

groomsman (noun)	attender (noun)
a male attendant of the bridegroom at a wedding	someone who waits on or tends to or attends to the needs of another
	a person who is present and participates in a meeting
	someone who listens attentively