graminaceous plant vs Poaceae

graminaceous plant and Poaceae both are nouns.

Word	Noun	Adjective	Verb	Adverb
graminaceous plant	Yes	No	No	No
Poaceae	Yes	No	No	No

graminaceous plant (noun)	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