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."

Definitions of onion
  1. noun
    bulbous plant having hollow leaves cultivated worldwide for its rounded edible bulb
    synonyms: Allium cepa, onion plant
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    Allium ascalonicum, Allium cepa aggregatum, eschalot, multiplier onion, shallot
    type of onion plant producing small clustered mild-flavored bulbs used as seasoning
    Allium cepa viviparum, Egyptian onion, top onion, tree onion
    type of perennial onion grown chiefly as a curiosity or for early salad onions; having bulbils that replace the flowers
    Allium fistulosum, Japanese leek, Welsh onion
    Asiatic onion with slender bulbs; used as early green onions
    Allium haematochiton, red-skinned onion
    onion with white to deep red tunic; California
    type of:
    alliaceous plant
    bulbous plants having a characteristic pungent onion odor
  2. noun
    an aromatic flavorful vegetable
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    Bermuda onion
    mild flat onion grown in warm areas
    green onion, scallion, spring onion
    a young onion before the bulb has enlarged; eaten in salads
    Vidalia onion
    sweet-flavored onion grown in Georgia
    Spanish onion
    large mild and succulent onion; often eaten raw
    small mild-flavored onion-like or garlic-like clustered bulbs used for seasoning
    purple onion, red onion
    flat mild onion having purplish tunics; used as garnish on hamburgers and salads
    type of:
    veg, vegetable, veggie
    edible seeds or roots or stems or leaves or bulbs or tubers or nonsweet fruits of any of numerous herbaceous plant
  3. noun
    the bulb of an onion plant
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    type of:
    a modified bud consisting of a thickened globular underground stem serving as a reproductive structure
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