dog grass vs witchgrass

dog grass and witchgrass both are nouns.

Word	Noun	Adjective	Verb	Adverb
dog grass	Yes	No	No	No
witchgrass	Yes	No	No	No

As nouns, dog grass and witchgrass are synonyms defined as:

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

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

dog grass (noun)	witchgrass (noun)
European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed	North American grass with slender brushy panicles; often a weed on cultivated land
	European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed