red ash vs Fraxinus pennsylvanica

red ash and Fraxinus pennsylvanica both are nouns.

Word	Noun	Adjective	Verb	Adverb
red ash	Yes	No	No	No
Fraxinus pennsylvanica	Yes	No	No	No

As nouns, red ash and Fraxinus pennsylvanica are synonyms defined as:

red ash and Fraxinus pennsylvanica: smallish American tree with velvety branchlets and lower leaf surfaces

Other synonyms of red ash include downy ash.

red ash (noun)	Fraxinus pennsylvanica (noun)
smallish American tree with velvety branchlets and lower leaf surfaces	smallish American tree with velvety branchlets and lower leaf surfaces