onion

American  

[uhn-yuhn] / ˈʌn jən /

noun

• onions
  plural

1. a plant, Allium cepa, of the amaryllis family, having an edible, succulent, pungent bulb.

2. any of certain similar plants.

3. the bulb of the onion plant.

4. the flavor or odor of this bulb.

5. Slang. a person.

   He's a tough onion.

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adjective

1. containing or cooked with onions.

   onion soup.

2. of, relating to, or resembling an onion.

idioms

1. know one's onions, to know one's subject or business thoroughly; be capable or proficient.

onion British  

/ ˈʌnjən /

noun

1. an alliaceous plant, Allium cepa, having greenish-white flowers: cultivated for its rounded edible bulb

2. the bulb of this plant, consisting of concentric layers of white succulent leaf bases with a pungent odour and taste

3. any of several related plants similar to A. cepa, such as A. fistulosum (Welsh onion)

4. slang to be fully acquainted with a subject

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onion More Idioms  

1. see know one's stuff (onions).

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Other Word Forms

Derived Forms

• onionlike
  adjective
• oniony
  adjective

Inflected Forms

Nouns

• onions
  plural

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Etymology

Origin of onion

1325–75; Middle English onyon < Old French oignon < Latin ūniōn- (stem of ūniō ) a unity, large pearl, onion; see union

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Explanation

An onion is a plant that grows as a bulb underground and can be harvested and eaten. Note: onions may be tasty, but they sure can make your breath stink. Onions are bulbs, like tulips or daffodils — most of the plant is hidden in the soil, with roots stretching down and stalks that grow upward and eventually bloom with small flowers. Onions are typically harvested in the fall, and they come in many shapes, sizes, and colors, all of which can be eaten. The Latin root of onion, unionem, was used in colloquial Roman to mean both "a type of onion" and "a pearl."

Example Sentences

See Examples For:

onion onions

I listened politely, nibbling my onion petals in a state of Zen-like detachment.

From Los Angeles Times ● Oct. 16, 2026

But he was also a mop, or a Vermeer, or a green onion, depending on whom you asked.

From The Wall Street Journal ● Oct. 8, 2026

Mine started with garlic, red onion, sun-dried tomatoes, cherry tomatoes, fennel, olive oil, spices and an anchovy or two, all piled into a Dutch oven and roasted together.

From Salon ● Sep. 28, 2026

Russ: I got all your favorites, sesame, onion, everything, plain.

From Los Angeles Times ● Sep. 21, 2026

Mama calls a girl in the front to turn the onion mixture into a thick paste using a potato masher.

From "A Place at the Table" by Saadia Faruqi and Laura Shovan

The host led us to a booth, steeped in the aroma of grilled onions.

From Los Angeles Times ● Oct. 16, 2026

Cargil and his son, Ryan, had spent months nursing crops of cabbage and onions to harvest.

From BBC ● Sep. 23, 2026

On Sunday, trucks carrying Iranian onions bound for Iraq were forced to turn back as a result, according to Tehran’s Central Fruit and Vegetable Market.

From The Wall Street Journal ● Sep. 17, 2026

Irrigation supports crops including alfalfa, cotton, onions, pecans, and the area's famous Hatch green chiles.

From Science Daily ● Sep. 3, 2026

“And once the onions are soft, we’ll add the tomatoes and spices to make a curry base.”

From "A Place at the Table" by Saadia Faruqi and Laura Shovan

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