birth rate vs birthrate

birth rate and birthrate both are nouns.

Word	Noun	Adjective	Verb	Adverb
birth rate	Yes	No	No	No
birthrate	Yes	No	No	No

As nouns, birth rate and birthrate are synonyms defined as:

birth rate and birthrate: the ratio of live births in an area to the population of that area; expressed per 1000 population per year

Other synonyms of birth rate include fertility, fertility rate, natality.

birth rate (noun)	birthrate (noun)
the ratio of live births in an area to the population of that area; expressed per 1000 population per year	the ratio of live births in an area to the population of that area; expressed per 1000 population per year