human death vs casualty

human death and casualty both are nouns.

Word	Noun	Adjective	Verb	Adverb
human death	Yes	No	No	No
casualty	Yes	No	No	No

As nouns, casualty is a hyponym of human death; that is, casualty is a word with a more specific, narrower meaning than human death:

Other hyponyms of human death include killing, violent death, fatal accident.

human death (noun)	casualty (noun)
a death resulting from an accident or a disaster	a decrease of military personnel or equipment
	an accident that causes someone to die
	someone injured or killed in an accident
	someone injured or killed or captured or missing in a military engagement