red-skinned onion vs onion

red-skinned onion and onion both are nouns.

Word	Noun	Adjective	Verb	Adverb
red-skinned onion	Yes	No	No	No
onion	Yes	No	No	No

As nouns, onion is a hypernym of red-skinned onion; that is, onion is a word with a broader meaning than red-skinned onion:

red-skinned onion: onion with white to deep red tunic; California
onion: bulbous plant having hollow leaves cultivated worldwide for its rounded edible bulb

Other hypernyms of red-skinned onion include Allium cepa, onion plant.

red-skinned onion (noun)	onion (noun)
onion with white to deep red tunic; California	an aromatic flavorful vegetable
	bulbous plant having hollow leaves cultivated worldwide for its rounded edible bulb
	the bulb of an onion plant