death rate vs mortality

death rate and mortality both are nouns.

Word	Noun	Adjective	Verb	Adverb
death rate	Yes	No	No	No
mortality	Yes	No	No	No

As nouns, death rate and mortality are synonyms defined as:

death rate and mortality: the ratio of deaths in an area to the population of that area; expressed per 1000 per year

Other synonyms of death rate include deathrate, fatality rate, mortality rate.

death rate (noun)	mortality (noun)
the ratio of deaths in an area to the population of that area; expressed per 1000 per year	the quality or state of being mortal
	the ratio of deaths in an area to the population of that area; expressed per 1000 per year