The onion, also known as the bulb onion or common onion, is a vegetable and is the most widely cultivated species of the genus Allium. This genus also contains several other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion the Egyptian onion and the Canada onion. The onion is most frequently a biennial or a perennial plant, but is usually treated as an annual and harvested in its first growing season.
