dead body vs mummy

dead body and mummy both are nouns.

Word	Noun	Adjective	Verb	Adverb
dead body	Yes	No	No	No
mummy	Yes	No	No	No

As nouns, mummy is a hyponym of dead body; that is, mummy is a word with a more specific, narrower meaning than dead body:

dead body: a natural object consisting of a dead animal or person
mummy: a body embalmed and dried and wrapped for burial (as in ancient Egypt)

Other hyponyms of dead body include kill, carcase, carcass, carrion, roadkill, cadaver, clay, corpse, remains, stiff.

dead body (noun)	mummy (noun)
a natural object consisting of a dead animal or person	a body embalmed and dried and wrapped for burial (as in ancient Egypt)
	informal terms for a mother