leaf beet vs leafy vegetable

leaf beet and leafy vegetable both are nouns.

Word	Noun	Adjective	Verb	Adverb
leaf beet	Yes	No	No	No
leafy vegetable	Yes	No	No	No

As nouns, leafy vegetable is a hypernym of leaf beet; that is, leafy vegetable is a word with a broader meaning than leaf beet:

leaf beet: long succulent whitish stalks with large green leaves
leafy vegetable: any of various leafy plants or their leaves and stems eaten as vegetables

Other hypernyms of leaf beet include green, greens.

leaf beet (noun)	leafy vegetable (noun)
long succulent whitish stalks with large green leaves	any of various leafy plants or their leaves and stems eaten as vegetables
beet lacking swollen root; grown as a vegetable for its edible leaves and stalks