sex activity vs extracurricular

sex activity is a noun but extracurricular is not a noun.

Word	Noun	Adjective	Verb	Adverb
sex activity	Yes	No	No	No
extracurricular	No	Yes	No	No

sex activity (noun)	extracurricular (noun)
activities associated with sexual intercourse

sex activity (adjective)	extracurricular (adjective)
	characterized by adultery
	outside the regular duties of your job or profession
	outside the regular academic curriculum