A walnut is the nut of any tree of the genus Juglans, particularly the Persian or English walnut. Walnuts are rounded, single-seeded stone fruits of the walnut tree commonly used for the meat after fully ripening. In India walnuts are grown in Arunachal Pradesh, Himachal Pradesh, Uttrakhand and Jammu and Kashmir.  Following full ripening, the removal of the husk reveals the wrinkly walnut shell, which is usually commercially found in two segments (three or four-segment shells can also form). During the ripening process, the husk will become brittle and the shell hard. The shell encloses the kernel or meat, which is usually made up of two halves separated by a partition. The seed kernels – commonly available as shelled walnuts – are enclosed in a brown seed coat which contains antioxidants.

After full ripening for its edible seed when the shell has been discarded, it is used as a garnish or a snack. Walnuts, like other tree nuts, must be processed and stored properly. Poor storage makes walnuts susceptible to insect and fungal mold infestations. A mold-infested walnut batch should be entirely discarded.