The medical term for having an extra finger or toe is polydactyly (pol-ee-dak-tuh-lee). The term literally means “extra digit.”
The extra digit may range from a small bump to a fully developed working finger or toe. Most often, it’s smaller than the other digits and not well formed. The manner in which the extra digit is formed and attached may influence how it is treated (see treatment options below).
Sometimes the extra digit is connected to the hand or foot with only a narrow piece of tissue. If the digit is better formed, it may have all the normal components (bone, muscles, blood vessels and nerves). If that is the case, it connects to the hand or foot deep inside.