Onions

The onion (Allium cepa), which is also known as the bulb onion, common onion and garden onion,^{[citation needed]} is the most widely cultivated species of the genus Allium. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion (A. fistulosum), Egyptian onion (A. ×proliferum), and Canada onion (A. canadense). The name "wild onion" is applied to a number of Allium species.

The vast majority of cultivars of A. cepa belong to the 'common onion group' (A. cepa var. cepa) and are usually referred to simply as 'onions'. The 'Aggregatum Group' of cultivars (A. cepa var. aggregatum) includes both shallots and potato onions.

Allium cepa is known only in cultivation, but related wild species occur in Central Asia. The most closely related species include Allium vavilovii (Popov & Vved.) and Allium asarense (R.M. Fritsch & Matin) from Iran. However, Zohary and Hopf warn that "there are doubts whether the A. vavilovii collections tested represent genuine wild material or only feral derivatives of the crop."

Onions are often chopped and used an ingredient in various hearty warm dishes, but are often used as a main ingredient in their own right, for example in French onion soup or onion chutney. They are also used raw in cold salads. Onions pickled in vinegar are eaten as a snack. These are often served as a side serving in fish and chip shops throughout the United Kingdom and Australia, often served with cheese in the United Kingdom, and as "pickled onions" in Eastern Europe. Fresh onion has a pungent, persistent, even irritating taste, but when sauteed, onion becomes sweet and much less pungent.