sex activity vs sexual activity

sex activity and sexual activity both are nouns.

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

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

sex activity and sexual activity: activities associated with sexual intercourse

Other synonyms of sex activity include sex, sexual practice.

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