quick grass vs Agropyron repens

quick grass and Agropyron repens both are nouns.

Word	Noun	Adjective	Verb	Adverb
quick grass	Yes	No	No	No
Agropyron repens	Yes	No	No	No

As nouns, quick grass and Agropyron repens are synonyms defined as:

quick grass and Agropyron repens: European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed

Other synonyms of quick grass include couch grass, dog grass, quack grass, quackgrass, witch grass, witchgrass.

quick grass (noun)	Agropyron repens (noun)
European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed	European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed