If you need to have surgery, a doctor will anesthetize you, or give you medicine to make you sleep through the operation.
When a vet knocks your dog out to clean his teeth, she anesthetizes him. Oral surgeons also anesthetize patients before removing their wisdom teeth. In both cases, special drugs are used to put the patient under, or make him sleep long enough for the procedure to be finished before he wakes up. A doctor whose job it is to anesthetize patients is called an anesthesiologist. The root word is Greek: anaisthesia, "lack of feeling or sensation."