Hypnosis (from the Greek hypnos, "sleep") is "a trance-like state that resembles sleep but is induced by a person whose suggestions are readily accepted by the subject."

The technique is used for medical purposes to relieve anxiety or otherwise improve or alter behaviour. It is also used in popular stage acts in which subjects are persuaded to perform bizarre feats.

Other variations include mass-hypnosis, in which crowds are simultaneously influenced, and autosuggestion in which a subject persuades themself.