bearded darnel vs rye grass

bearded darnel and rye grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
bearded darnel	Yes	No	No	No
rye grass	Yes	No	No	No

As nouns, rye grass is a hypernym of bearded darnel; that is, rye grass is a word with a broader meaning than bearded darnel:

bearded darnel: weedy annual grass often occurs in grainfields and other cultivated land; seeds sometimes considered poisonous
rye grass: any of several annual or perennial Eurasian grasses

Other hypernyms of bearded darnel include ryegrass.

bearded darnel (noun)	rye grass (noun)
weedy annual grass often occurs in grainfields and other cultivated land; seeds sometimes considered poisonous	any of several annual or perennial Eurasian grasses