bisexuality vs sexual activity

bisexuality and sexual activity both are nouns.

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

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

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

bisexuality (noun)	sexual activity (noun)
sexual activity with both men and women	activities associated with sexual intercourse
showing characteristics of both sexes