pairing vs sex activity

pairing and sex activity both are nouns.

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

As nouns, sex activity is a hypernym of pairing; that is, sex activity is a word with a broader meaning than pairing:

Other hypernyms of pairing include sex, sexual activity, sexual practice.

pairing (noun)	sex activity (noun)
the act of pairing a male and female for reproductive purposes	activities associated with sexual intercourse
the act of grouping things or people in pairs