sexual activity vs promiscuous

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

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

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

sexual activity (adjective)	promiscuous (adjective)
	not selective of a single class or person
	casual and unrestrained in sexual behavior