sexual activity vs sex activity

sexual activity and sex activity both are nouns.

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

As nouns, sexual activity and sex activity are synonyms defined as:

sexual activity and sex activity: activities associated with sexual intercourse

Other synonyms of sexual activity include sex, sexual practice.

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