downy ash vs green ash

downy ash and green ash both are nouns.

Word	Noun	Adjective	Verb	Adverb
downy ash	Yes	No	No	No
green ash	Yes	No	No	No

As nouns, green ash is a hyponym of downy ash; that is, green ash is a word with a more specific, narrower meaning than downy ash:

downy ash: smallish American tree with velvety branchlets and lower leaf surfaces
green ash: a variety of red ash having glossy branchlets and lower leaf surfaces

Other hyponyms of downy ash include Fraxinus pennsylvanica subintegerrima.

downy ash (noun)	green ash (noun)
smallish American tree with velvety branchlets and lower leaf surfaces	a variety of red ash having glossy branchlets and lower leaf surfaces