prosthesis

Imagine a sailor losing a leg at sea. An artificial leg, once a simple wooden peg and now often made with metal, plastic, or carbon fiber, could help them walk again. That is the central idea of this word: an artificial device that replaces a missing body part or helps restore its function. People most often use it for arms and legs, but it can also describe things like an artificial eye, a dental replacement, or another medical replacement placed in the body.

A prosthesis (pronounced pros-THEE-sis) is an artificial device used to replace a missing body part or to help restore its function. People usually use the word in medicine, especially for artificial arms, legs, hands, feet, eyes, teeth, breasts, joints, or other body parts that have been lost, damaged, or did not fully develop.

Historically, these devices were often simple, such as wooden legs, hooks for hands, or basic false teeth. Today, they can be far more advanced. Modern versions may use lightweight materials, careful engineering, sensors, and computer controls to improve movement, comfort, and daily use. Some are designed mainly to restore appearance, while others are built to improve practical function, such as walking, gripping, or chewing.

The word can sometimes appear in a broader or more technical sense for something added to make up for what is missing, but that is less common in everyday English. In normal use, it strongly points to a medical replacement for a body part.

The word comes from Greek and originally carried the idea of an "addition." That history fits the modern meaning well: something is added to the body to replace what is missing and to help a person live more fully.