Lolium temulentum vs ryegrass

Lolium temulentum and ryegrass both are nouns.

Word	Noun	Adjective	Verb	Adverb
Lolium temulentum	Yes	No	No	No
ryegrass	Yes	No	No	No

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

Lolium temulentum: 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 Lolium temulentum include rye grass.

Lolium temulentum (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