veg vs onion

veg and onion both are nouns.

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

As nouns, onion is a hyponym of veg; that is, onion is a word with a more specific, narrower meaning than veg:

veg: edible seeds or roots or stems or leaves or bulbs or tubers or nonsweet fruits of any of numerous herbaceous plant
onion: an aromatic flavorful vegetable

veg (noun)	onion (noun)
edible seeds or roots or stems or leaves or bulbs or tubers or nonsweet fruits of any of numerous herbaceous plant	an aromatic flavorful vegetable
	bulbous plant having hollow leaves cultivated worldwide for its rounded edible bulb
	the bulb of an onion plant