sexual activity vs arouse

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

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

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

sexual activity (verb)	arouse (verb)
	cause to be alert and energetic
	cause to become awake or conscious
	stop sleeping
	summon into action or bring into existence, often as if by magic
	call forth (emotions, feelings, and responses)
	to evoke sexual feelings
	to begin moving