tonka bean, black-skinned, aromatic, almondlike single seed from the pod of any tall leguminous tree of the genus Dipteryx in the family Leguminosae (pulse family) of tropical South America. It contains coumarin, a fermented substance that has a vanillalike aroma and is used as a vanilla substitute and in the manufacture of perfumes, sachets, soaps, tobacco, and food. Natural coumarin has been almost completely replaced by a synthetic product. The name of the bean also appears as tonqua bean and tonquin bean. Plants producing tonka beans are classified in the division Magnoliophyta, class Magnoliopsida, order Rosales, family Leguminosae.