A walnut is the edible seed of a drupe of any tree of the genus Juglans, particularly the Persian or English walnut, Juglans regia.
Although culinarily considered a "nut" and used as such, it is not a true botanical nut. After full ripening, the shell is discarded and the kernel is eaten. Nuts of the eastern black walnut (Juglans nigra) and butternuts (Juglans cinerea) are less commonly consumed.