greens vs veg

greens and veg both are nouns.

Word	Noun	Adjective	Verb	Adverb
greens	Yes	No	No	No
veg	Yes	No	No	No

As nouns, veg is a hypernym of greens; that is, veg is a word with a broader meaning than greens:

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

Other hypernyms of greens include vegetable, veggie.

greens (noun)	veg (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