sorb apple vs mountain ash

sorb apple and mountain ash both are nouns.

Word	Noun	Adjective	Verb	Adverb
sorb apple	Yes	No	No	No
mountain ash	Yes	No	No	No

As nouns, mountain ash is a hypernym of sorb apple; that is, mountain ash is a word with a broader meaning than sorb apple:

sorb apple: medium-sized European tree resembling the rowan but bearing edible fruit
mountain ash: any of various trees of the genus Sorbus

sorb apple (noun)	mountain ash (noun)
acid gritty-textured fruit	any of various trees of the genus Sorbus
medium-sized European tree resembling the rowan but bearing edible fruit	low-growing ash of Texas
	tree having wood similar to the alpine ash; tallest tree in Australia and tallest hardwood in the world