gramineous plant vs family Poaceae

gramineous plant and family Poaceae both are nouns.

Word	Noun	Adjective	Verb	Adverb
gramineous plant	Yes	No	No	No
family Poaceae	Yes	No	No	No

gramineous plant (noun)	family Poaceae (noun)
cosmopolitan herbaceous or woody plants with hollow jointed stems and long narrow leaves	the grasses: chiefly herbaceous but some woody plants including cereals, bamboo, reeds, sugar cane