Trifolium dubium vs trefoil

Trifolium dubium and trefoil both are nouns.

Word	Noun	Adjective	Verb	Adverb
Trifolium dubium	Yes	No	No	No
trefoil	Yes	No	No	No

As nouns, trefoil is a hypernym of Trifolium dubium; that is, trefoil is a word with a broader meaning than Trifolium dubium:

Trifolium dubium: clover native to Ireland with yellowish flowers; often considered the true or original shamrock
trefoil: a plant of the genus Trifolium

Other hypernyms of Trifolium dubium include clover.

Trifolium dubium (noun)	trefoil (noun)
clover native to Ireland with yellowish flowers; often considered the true or original shamrock	an architectural ornament in the form of three arcs arranged in a circle
	a plant of the genus Trifolium
	any of several Old World herbs of the genus Medicago having small flowers and trifoliate compound leaves