Mustard (or "prepared mustard") is a condiment made from the seeds of a mustard plant, or, more rarely, a name for the mustard plant itself. When the leaves of members of the mustard family are used as a vegetable, they are called mustard greens. In its whole and ground forms, mustard is one of the most widely used spices and condiments in the world.
Several variants of the mustard plant are cultivated, including white or yellow mustard (Sinapis alba), brown mustard (Brassica juncea), and black mustard (Brassica nigra). In European and American cuisine, the most common preparation of mustard is a mixture of finely or coarsely ground seeds with acidic liquids including vinegar, lemon juice, and wine, and salt, and when recipes refer to "mustard" they usually mean this preparation.