leafy vegetable vs veggie

leafy vegetable and veggie both are nouns.

Word	Noun	Adjective	Verb	Adverb
leafy vegetable	Yes	No	No	No
veggie	Yes	No	No	No

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

leafy vegetable: any of various leafy plants or their leaves and stems eaten as vegetables
veggie: edible seeds or roots or stems or leaves or bulbs or tubers or nonsweet fruits of any of numerous herbaceous plant

Other hypernyms of leafy vegetable include veg, vegetable.

leafy vegetable (noun)	veggie (noun)
any of various leafy plants or their leaves and stems eaten as vegetables	edible seeds or roots or stems or leaves or bulbs or tubers or nonsweet fruits of any of numerous herbaceous plant