deceased person vs someone

deceased person and someone both are nouns.

Word	Noun	Adjective	Verb	Adverb
deceased person	Yes	No	No	No
someone	Yes	No	No	No

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

deceased person: someone who is no longer alive
someone: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

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

deceased person (noun)	someone (noun)
someone who is no longer alive	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential