An anesthetic or anaesthetic is a substance that stops pain. It makes people either stop hurting, or go completely to sleep during surgery. Anesthetic can be rubbed onto the skin, given by injection ("shot"), or given as a gas to breathe. The use of an anesthetic is called anaesthesia. Anaesthesia blocks the pain during operations. This lets patients undergo surgery and other procedures without the distress and pain they would normally feel. It comes from Greek roots an-, "without" and aesthetos, "perceptible, able to feel".