lovemaking vs sexual activity

lovemaking and sexual activity both are nouns.

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

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

lovemaking: sexual activities (often including sexual intercourse) between two people
sexual activity: activities associated with sexual intercourse

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

lovemaking (noun)	sexual activity (noun)
sexual activities (often including sexual intercourse) between two people	activities associated with sexual intercourse