Anesthesia

Anesthesia, or anaesthesia (see spelling differences; from Greek "without"; and  "sensation"), has traditionally meant the condition of having sensation (including the feeling of pain) blocked or temporarily taken away. It is a pharmacologically induced reversible state of amnesia, analgesia, loss of responsiveness, loss of skeletal muscle reflexes and/or decreased stress response. This allows patients to undergo surgery and other procedures without the distress and pain they would otherwise experience. The word was coined by Oliver Wendell Holmes, Sr. in 1846.  Another definition is a "reversible lack of awareness," whether this is a total lack of awareness (e.g. a general anesthetic) or a lack of awareness of a part of the body such as a spinal anesthetic or another nerve block would cause.