Agrostis alba vs meadowgrass

Agrostis alba and meadowgrass both are nouns.

Word	Noun	Adjective	Verb	Adverb
Agrostis alba	Yes	No	No	No
meadowgrass	Yes	No	No	No

As nouns, meadowgrass is a hypernym of Agrostis alba; that is, meadowgrass is a word with a broader meaning than Agrostis alba:

Agrostis alba: slender European grass of shady places; grown also in northeastern America and temperate Asia
meadowgrass: any of various grasses that thrive in the presence of abundant moisture

Other hypernyms of Agrostis alba include meadow grass.

Agrostis alba (noun)	meadowgrass (noun)
slender European grass of shady places; grown also in northeastern America and temperate Asia	any of various grasses that thrive in the presence of abundant moisture