black elderberry vs American elder

black elderberry and American elder both are nouns.

Word	Noun	Adjective	Verb	Adverb
black elderberry	Yes	No	No	No
American elder	Yes	No	No	No

As nouns, black elderberry and American elder are synonyms defined as:

black elderberry and American elder: common elder of central and eastern North America bearing purple-black berries; fruit used in wines and jellies

Other synonyms of black elderberry include Sambucus canadensis, sweet elder.

black elderberry (noun)	American elder (noun)
common elder of central and eastern North America bearing purple-black berries; fruit used in wines and jellies	common elder of central and eastern North America bearing purple-black berries; fruit used in wines and jellies