Bromus tectorum vs brome

Bromus tectorum and brome both are nouns.

Word	Noun	Adjective	Verb	Adverb
Bromus tectorum	Yes	No	No	No
brome	Yes	No	No	No

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

Bromus tectorum: annual or winter annual grass with softly hairy leaves of the Mediterranean
brome: any of various woodland and meadow grasses of the genus Bromus; native to temperate regions

Other hypernyms of Bromus tectorum include bromegrass.

Bromus tectorum (noun)	brome (noun)
annual or winter annual grass with softly hairy leaves of the Mediterranean	any of various woodland and meadow grasses of the genus Bromus; native to temperate regions