corn speedwell vs speedwell

corn speedwell and speedwell both are nouns.

Word	Noun	Adjective	Verb	Adverb
corn speedwell	Yes	No	No	No
speedwell	Yes	No	No	No

As nouns, speedwell is a hypernym of corn speedwell; that is, speedwell is a word with a broader meaning than corn speedwell:

corn speedwell: erect or procumbent blue-flowered annual found in waste places of Europe and America
speedwell: any plant of the genus Veronica

Other hypernyms of corn speedwell include veronica.

corn speedwell (noun)	speedwell (noun)
erect or procumbent blue-flowered annual found in waste places of Europe and America	any plant of the genus Veronica