Onion

The onion, also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus Allium, whose close relatives include garlic, scallion, leek and chives; the shallot is a botanical variety of the onion that was classified as a separate species until 2011. The genus also contains several other cultivated food species, such as the Japanese bunching onion, the tree onion and the Canada onion, and while the term wild onion is applied to a number of Allium species, the common onion itself is known exclusively from cultivation, its ancestral wild form unidentified, though plants that have escaped cultivation have become established in some regions. The onion is most often a biennial or perennial plant but is usually grown and harvested as an annual.