bent grass vs genus Agrostis

bent grass and genus Agrostis both are nouns.

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

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