cashew (kăshˈō, kəshōˈ) [key], tropical American tree ( Anacardium occidentale ) of the family Anacardiaceae (sumac family), valued chiefly for the cashew nut of commerce. The tree's acrid sap is used in making a varnish that protects woodwork and books from insects. The fruit is kidney-shaped, about an inch in length, and has a double shell. The kernel, which is sweet, oily, and nutritious, is much used for food in the tropics after being roasted to destroy the caustic juice. It yields a light-colored oil said to be the equal of olive oil and is utilized in various culinary ways. In the West Indies it is used to flavor wine, particularly Madeira, and is imported into Great Britain for this purpose. The nut grows on the end of a fleshy, pear-shaped stalk, called the cashew apple, which is white, yellow, or red, juicy and slightly acid, and is eaten or fermented to make wine. Cashews are classified in the division Magnoliophyta, class Magnoliopsida, order Sapindales, family Anacardiaceae.