Polydactyly

Polydactyly or polydactylism (from the Greek poly = "many" + daktylos = "finger"), also known as hyperdactyly, is a congenital physical anomaly consisting of supernumerary fingers or toes. The extra digit is usually a small piece of soft tissue; occasionally it may contain bone without joints; rarely it may be a complete, functioning digit. The extra digit is most common on the ulnar side of the hand, less common on the radial side, and very rarely within the middle three digits. The extra digit is most commonly an abnormal fork in an existing digit, or it may rarely originate at the wrist like a normal digit does.