cumfrey vs herb

cumfrey and herb both are nouns.

Word	Noun	Adjective	Verb	Adverb
cumfrey	Yes	No	No	No
herb	Yes	No	No	No

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

cumfrey: perennial herbs of Europe and Iran; make rapidly growing groundcover for shaded areas
herb: a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests

Other hypernyms of cumfrey include herbaceous plant.

cumfrey (noun)	herb (noun)
perennial herbs of Europe and Iran; make rapidly growing groundcover for shaded areas	aromatic potherb used in cookery for its savory qualities
	a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests