Amputation is the removal of a body extremity by trauma or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on individuals as a preventative surgery for such problems. A special case is the congenital amputation, a congenital disorder, where foetal limbs have been cut off by constrictive bands. In some countries, amputation of the hands or feet is or was used as a form of punishment for people who committed crimes. Amputation has also been used as a tactic in war and acts of terrorism. In some cultures and religions, minor amputations or mutilations are considered a ritual accomplishment. Unlike many non-mammalian animals (such as lizards that shed their tails), once removed, human extremities do not grow back. A transplant or a prosthesis is the only option for recovering the loss.

From http://en.wikipedia.org/wiki/Amputation