downy poplar vs black cottonwood

downy poplar and black cottonwood both are nouns.

Word	Noun	Adjective	Verb	Adverb
downy poplar	Yes	No	No	No
black cottonwood	Yes	No	No	No

As nouns, downy poplar and black cottonwood are synonyms defined as:

downy poplar and black cottonwood: North American poplar with large rounded scalloped leaves and brownish bark and wood

Other synonyms of downy poplar include Populus heterophylla, swamp cottonwood, swamp poplar.

downy poplar (noun)	black cottonwood (noun)
North American poplar with large rounded scalloped leaves and brownish bark and wood	cottonwood of western North America with dark green leaves shining above and rusty or silvery beneath
	North American poplar with large rounded scalloped leaves and brownish bark and wood