Irish potato vs root vegetable

Irish potato and root vegetable both are nouns.

Word	Noun	Adjective	Verb	Adverb
Irish potato	Yes	No	No	No
root vegetable	Yes	No	No	No

As nouns, root vegetable is a hypernym of Irish potato; that is, root vegetable is a word with a broader meaning than Irish potato:

Irish potato: an edible tuber native to South America; a staple food of Ireland
root vegetable: any of various fleshy edible underground roots or tubers

Other hypernyms of Irish potato include starches, solanaceous vegetable.

Irish potato (noun)	root vegetable (noun)
an edible tuber native to South America; a staple food of Ireland	any of various fleshy edible underground roots or tubers