black willow vs swamp willow

black willow and swamp willow both are nouns.

Word	Noun	Adjective	Verb	Adverb
black willow	Yes	No	No	No
swamp willow	Yes	No	No	No

As nouns, black willow and swamp willow are synonyms defined as:

black willow and swamp willow: North American shrubby willow having dark bark and linear leaves growing close to streams and lakes

Other synonyms of black willow include Salix nigra.

black willow (noun)	swamp willow (noun)
North American shrubby willow having dark bark and linear leaves growing close to streams and lakes	North American shrubby willow having dark bark and linear leaves growing close to streams and lakes