herba impia vs cudweed

herba impia and cudweed both are nouns.

Word	Noun	Adjective	Verb	Adverb
herba impia	Yes	No	No	No
cudweed	Yes	No	No	No

As nouns, cudweed is a hypernym of herba impia; that is, cudweed is a word with a broader meaning than herba impia:

herba impia: (literally an undutiful herb) a variety of cotton rose
cudweed: any plant of the genus Filago having capitate clusters of small woolly flower heads

Other hypernyms of herba impia include cotton rose, filago.

herba impia (noun)	cudweed (noun)
(literally an undutiful herb) a variety of cotton rose	any of numerous plants of the genus Gnaphalium having flowers that can be dried without loss of form or color
	any plant of the genus Filago having capitate clusters of small woolly flower heads
	perennial cottony-white herb of southwestern United States