Pennisetum Americanum vs genus Pennisetum

Pennisetum Americanum and genus Pennisetum both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pennisetum Americanum	Yes	No	No	No
genus Pennisetum	Yes	No	No	No

Pennisetum Americanum (noun)	genus Pennisetum (noun)
tall grass having cattail like spikes; grown in Africa and Asia for its grain and in the United States chiefly for forage; sometimes used in making beer	a genus of Old World grasses