darnel vs ryegrass

darnel and ryegrass both are nouns.

Word	Noun	Adjective	Verb	Adverb
darnel	Yes	No	No	No
ryegrass	Yes	No	No	No

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

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

Other hypernyms of darnel include rye grass.

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