The leek is a vegetable, a cultivar of Allium ampeloprasum, the broadleaf wild leek. The edible part of the plant is a bundle of leaf sheaths that is sometimes erroneously called a stem or stalk. The genus Allium also contains the onion, garlic, shallot, scallion, chive, and Chinese onion.
Three closely related vegetables, elephant garlic, kurrat and Persian leek or tareh, are also cultivars of A. ampeloprasum, although different in their uses as food.