common comfrey vs cumfrey

common comfrey and cumfrey both are nouns.

Word	Noun	Adjective	Verb	Adverb
common comfrey	Yes	No	No	No
cumfrey	Yes	No	No	No

As nouns, cumfrey is a hypernym of common comfrey; that is, cumfrey is a word with a broader meaning than common comfrey:

common comfrey: European herb having small white, pink or purple flowers; naturalized as a weed in North America
cumfrey: perennial herbs of Europe and Iran; make rapidly growing groundcover for shaded areas

Other hypernyms of common comfrey include comfrey.

common comfrey (noun)	cumfrey (noun)
European herb having small white, pink or purple flowers; naturalized as a weed in North America	perennial herbs of Europe and Iran; make rapidly growing groundcover for shaded areas