common burdock vs clotbur

common burdock and clotbur both are nouns.

Word	Noun	Adjective	Verb	Adverb
common burdock	Yes	No	No	No
clotbur	Yes	No	No	No

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

common burdock: a plant that is ubiquitous in all but very acid soil; found in most of Europe and North Africa
clotbur: any of several erect biennial herbs of temperate Eurasia having stout taproots and producing burs

Other hypernyms of common burdock include burdock.

common burdock (noun)	clotbur (noun)
a plant that is ubiquitous in all but very acid soil; found in most of Europe and North Africa	any of several erect biennial herbs of temperate Eurasia having stout taproots and producing burs