neonatal mortality vs deathrate

neonatal mortality and deathrate both are nouns.

Word	Noun	Adjective	Verb	Adverb
neonatal mortality	Yes	No	No	No
deathrate	Yes	No	No	No

As nouns, deathrate is a hypernym of neonatal mortality; that is, deathrate is a word with a broader meaning than neonatal mortality:

neonatal mortality: the death rate during the first 28 days of life
deathrate: the ratio of deaths in an area to the population of that area; expressed per 1000 per year

Other hypernyms of neonatal mortality include death rate, fatality rate, mortality, mortality rate.

neonatal mortality (noun)	deathrate (noun)
the death rate during the first 28 days of life	the ratio of deaths in an area to the population of that area; expressed per 1000 per year