dead person vs mortal

dead person and mortal both are nouns.

Word	Noun	Adjective	Verb	Adverb
dead person	Yes	No	No	No
mortal	Yes	Yes	No	No

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

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

Other hypernyms of dead person include individual, person, somebody, someone, soul.

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

dead person (adjective)	mortal (adjective)
	subject to death
	unrelenting and deadly
	involving loss of divine grace or spiritual death
	causing or capable of causing death