hexadactyly

hexadactyly The presence of an extra digit: a sixth finger or toe. Hexadactyly is a very common birth defect. The sixth digit can be located in three different locations: on either side of the extremity or somewhere in between. With the hand, for example, the extra finger can be out beyond the little finger (ulnar hexadactyly), out beyond the thumb (radial hexadactyly), or between two of the normally expected fingers (intercalary hexadactyly). See also polydactyly.