black cottonwood vs downy poplar

black cottonwood and downy poplar both are nouns.

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

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

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

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

black cottonwood (noun)	downy poplar (noun)
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
North American poplar with large rounded scalloped leaves and brownish bark and wood