genus Agrostis vs bent grass

genus Agrostis and bent grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
genus Agrostis	Yes	No	No	No
bent grass	Yes	No	No	No

genus Agrostis (noun)	bent grass (noun)
annual or perennial grasses cosmopolitan in Northern Hemisphere: bent grass (so named from `bent' meaning an area of unfenced grassland)	grass for pastures and lawns especially bowling and putting greens