right hander vs someone

right hander and someone both are nouns.

Word	Noun	Adjective	Verb	Adverb
right hander	Yes	No	No	No
someone	Yes	No	No	No

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

right hander: a person who uses the right hand more skillfully than the left
someone: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

Other hypernyms of right hander include individual, mortal, person, somebody, soul.

right hander (noun)	someone (noun)
a person who uses the right hand more skillfully than the left	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential