sexual activity vs filthy

sexual activity is a noun but filthy is not a noun.

Word	Noun	Adjective	Verb	Adverb
sexual activity	Yes	No	No	No
filthy	No	Yes	No	No

sexual activity (noun)	filthy (noun)
activities associated with sexual intercourse

sexual activity (adjective)	filthy (adjective)
	disgustingly dirty; filled or smeared with offensive matter
	characterized by obscenity
	vile; despicable