What is the name of the birth defect characterized by having extra digits?

Polydactylism refers to a condition where an individual is born with extra digits, which can occur in the hands or feet. This genetic condition may involve entirely formed additional fingers or toes, or it can present as a simple skin tag or an incomplete digit. The term comes from the Greek words "poly," meaning many, and "daktylos," meaning fingers.

In contrast, phocomelia is a congenital condition characterized by the malformation of limbs, resulting in extremely short or absent arms and legs, often due to teratogenic effects during pregnancy. Hemangioma refers to a benign tumor made up of blood vessels, commonly found on the skin, and does not involve the characteristic of having extra digits. Hypertrophy is the enlargement of an organ or tissue through the increase in the size of its cells and does not relate specifically to the presence of additional digits. Thus, polydactylism accurately describes the birth defect associated with having extra fingers or toes.