gayness vs sexual activity

gayness and sexual activity both are nouns.

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

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

gayness: a sexual attraction to (or sexual relations with) persons of the same sex
sexual activity: activities associated with sexual intercourse

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

gayness (noun)	sexual activity (noun)
a sexual attraction to (or sexual relations with) persons of the same sex	activities associated with sexual intercourse