heterosexual vs someone

heterosexual and someone both are nouns.

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

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

heterosexual: a person having a sexual orientation to persons of the opposite sex
someone: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

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

heterosexual (noun)	someone (noun)
a person having a sexual orientation to persons of the opposite sex	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

heterosexual (adjective)	someone (adjective)
sexually attracted to members of the opposite sex