smooth alder vs hazel alder

smooth alder and hazel alder both are nouns.

Word	Noun	Adjective	Verb	Adverb
smooth alder	Yes	No	No	No
hazel alder	Yes	No	No	No

As nouns, smooth alder and hazel alder are synonyms defined as:

smooth alder and hazel alder: common shrub of the eastern United States with smooth bark

Other synonyms of smooth alder include Alnus serrulata.

smooth alder (noun)	hazel alder (noun)
common shrub of the eastern United States with smooth bark	common shrub of the eastern United States with smooth bark