black ash vs brown ash

black ash and brown ash both are nouns.

Word	Noun	Adjective	Verb	Adverb
black ash	Yes	No	No	No
brown ash	Yes	No	No	No

As nouns, black ash and brown ash are synonyms defined as:

black ash and brown ash: vigorous spreading North American tree having dark brown heavy wood; leaves turn gold in autumn

Other synonyms of black ash include basket ash, Fraxinus nigra, hoop ash.

black ash (noun)	brown ash (noun)
vigorous spreading North American tree having dark brown heavy wood; leaves turn gold in autumn	vigorous spreading North American tree having dark brown heavy wood; leaves turn gold in autumn