Use the adjective prosthetic to describe something that has to do with an artificial body part. You might know someone who walks with the help of a prosthetic leg.
Something that's prosthetic fills in for a missing part. In some cases, people are born without an arm or a foot, and in others they've lost a limb in an accident. Prosthetic limbs can help them get along more easily, substituting for the absent part. Prosthetic has a Greek root, prostithenai, or "addition," and an early meaning of "that which is added to the body."