onion | plant | Britannica
onion, (Allium cepa), herbaceous biennial plant in the amaryllis family (Amaryllidaceae), grown for its edible bulb. The onion is likely native to southwestern Asia but is now grown throughout the world, chiefly in the temperate zones. Onions are low in nutrients but are valued for their flavour and are used widely in cooking. They add flavour to such dishes as stews, roasts, soups, and salads and are also served as a cooked vegetable. The common onion has one or more leafless flower stalks that reach a height of 75–180 cm (2.5–6 feet), terminating in a spherical cluster of small greenish