Anaesthesia comes from the Greek word
which means insensibility. Today it is used to mean loss of sensation with or without loss of consciousness. More specifically, it describes the condition of having sensation, including the feeling of pain, being blocked. Most of us are familiar with local anaesthesia applied through an injection before dental treatment like a filling or a root canal treatment. General anaesthesia which is a pharmacologically induced state, allows patients to undergo surgery without the pain they would otherwise experience. Oliver Wendell Holmes first used the term anesthesia in 1846 to describe drug-induced insensibility to sensation (particularly pain) following the demonstration of inhaled ether rendering a patient unresponsive during a surgical procedure .