swamp poplar vs black cottonwood

swamp poplar and black cottonwood both are nouns.

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

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

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

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

swamp 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