dog grass vs Agropyron repens

dog grass and Agropyron repens both are nouns.

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

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

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

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

dog 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