coupling vs sexual activity

coupling and sexual activity both are nouns.

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

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

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

coupling (noun)	sexual activity (noun)
the act of pairing a male and female for reproductive purposes	activities associated with sexual intercourse
a mechanical device that serves to connect the ends of adjacent objects
a connection (like a clamp or vise) between two things so they move together