/ ˈʌnjən; NAmE / noun
[ C , U ] a round vegetable with many layers inside each other and a brown, red or white skin. Onions have a strong smell and flavour :
Chop the onions finely.
French onion soup
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WORD ORIGIN
Middle English : from Old French oignon , based on Latin unio(n-) , denoting a kind of onion.