menial vs retainer

menial and retainer both are nouns.

Word	Noun	Adjective	Verb	Adverb
menial	Yes	Yes	No	No
retainer	Yes	No	No	No

As nouns, retainer is a hypernym of menial; that is, retainer is a word with a broader meaning than menial:

menial: a domestic servant
retainer: a person working in the service of another (especially in the household)

Other hypernyms of menial include servant.

menial (noun)	retainer (noun)
a domestic servant	a dental appliance that holds teeth (or a prosthesis) in position after orthodontic treatment
	a person working in the service of another (especially in the household)
	a fee charged in advance to retain the services of someone

menial (adjective)	retainer (adjective)
used of unskilled work (especially domestic work)