onion vs onion plant

onion and onion plant both are nouns.

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

As nouns, onion and onion plant are synonyms defined as:

onion and onion plant: bulbous plant having hollow leaves cultivated worldwide for its rounded edible bulb

Other synonyms of onion include Allium cepa.

onion (noun)	onion plant (noun)
an aromatic flavorful vegetable	bulbous plant having hollow leaves cultivated worldwide for its rounded edible bulb
bulbous plant having hollow leaves cultivated worldwide for its rounded edible bulb
the bulb of an onion plant