stays vs foundation garment

stays and foundation garment both are nouns.

Word	Noun	Adjective	Verb	Adverb
stays	Yes	No	No	No
foundation garment	Yes	No	No	No

As nouns, foundation garment is a hypernym of stays; that is, foundation garment is a word with a broader meaning than stays:

stays: a woman's close-fitting foundation garment
foundation garment: a woman's undergarment worn to give shape to the contours of the body

Other hypernyms of stays include foundation.

stays (noun)	foundation garment (noun)
a woman's close-fitting foundation garment	a woman's undergarment worn to give shape to the contours of the body