homosexual vs someone

homosexual and someone both are nouns.

Word	Noun	Adjective	Verb	Adverb
homosexual	Yes	Yes	No	No
someone	Yes	No	No	No

As nouns, someone is a hypernym of homosexual; that is, someone is a word with a broader meaning than homosexual:

homosexual: someone who is sexually attracted to persons of the same sex
someone: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

Other hypernyms of homosexual include individual, mortal, person, somebody, soul.

homosexual (noun)	someone (noun)
someone who is sexually attracted to persons of the same sex	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

homosexual (adjective)	someone (adjective)
sexually attracted to members of your own sex