redheader vs someone

redheader and someone both are nouns.

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

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

redheader: someone who has red hair
someone: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

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

redheader (noun)	someone (noun)
someone who has red hair	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential