Bromus secalinus vs bromegrass

Bromus secalinus and bromegrass both are nouns.

Word	Noun	Adjective	Verb	Adverb
Bromus secalinus	Yes	No	No	No
bromegrass	Yes	No	No	No

As nouns, bromegrass is a hypernym of Bromus secalinus; that is, bromegrass is a word with a broader meaning than Bromus secalinus:

Bromus secalinus: weedy annual native to Europe but widely distributed as a weed especially in wheat
bromegrass: any of various woodland and meadow grasses of the genus Bromus; native to temperate regions

Other hypernyms of Bromus secalinus include brome.

Bromus secalinus (noun)	bromegrass (noun)
weedy annual native to Europe but widely distributed as a weed especially in wheat	any of various woodland and meadow grasses of the genus Bromus; native to temperate regions