A walnut is the nut of any tree of the genus Juglans (family Juglandaceae), particularly the Persian or English walnut, Juglans regia. A walnut is the edible seed of a drupe and thus not a true botanical nut. It is commonly consumed as a nut. After full ripening for its edible seed, it is used as a garnish or a snack when the shell has been discarded. Nuts of the eastern black walnut (Juglans nigra) and butternuts (Juglans cinerea) are less commonly consumed.
A nut is a fruit composed of a hard shell and a seed, which is generally edible.
There is an additional requirement in botany that the shell does not open to release the seed (indehiscent). In a general context, a wide variety of dried seeds are called nuts, but in a botanical context, only ones that include the indehiscent fruit are considered true nuts.