mountain avens vs subshrub

mountain avens and subshrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
mountain avens	Yes	No	No	No
subshrub	Yes	No	No	No

As nouns, subshrub is a hypernym of mountain avens; that is, subshrub is a word with a broader meaning than mountain avens:

mountain avens: creeping evergreen shrub with large white flowers; widely distributed in northern portions of Eurasia and North America
subshrub: low-growing woody shrub or perennial with woody base

Other hypernyms of mountain avens include suffrutex.

mountain avens (noun)	subshrub (noun)
creeping evergreen shrub with large white flowers; widely distributed in northern portions of Eurasia and North America	low-growing woody shrub or perennial with woody base