kept woman vs woman

kept woman and woman both are nouns.

Word	Noun	Adjective	Verb	Adverb
kept woman	Yes	No	No	No
woman	Yes	No	No	No

As nouns, woman is a hypernym of kept woman; that is, woman is a word with a broader meaning than kept woman:

kept woman: an adulterous woman; a woman who has an ongoing extramarital sexual relationship with a man
woman: an adult female person (as opposed to a man)

Other hypernyms of kept woman include lover, adult female.

kept woman (noun)	woman (noun)
an adulterous woman; a woman who has an ongoing extramarital sexual relationship with a man	women as a class
	an adult female person (as opposed to a man)
	a female person who plays a significant role (wife or mistress or girlfriend) in the life of a particular man