spinach beet vs leafy vegetable

spinach beet and leafy vegetable both are nouns.

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

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

spinach 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 spinach beet include green, greens.

spinach 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