Hypnosis is altered state of consciousness in which the hypnotized individual is more susceptible to suggestion. It is induced by a procedure known as a hypnotic induction, which is a long series of preliminary instructions and suggestions. These suggestions are either delivered by a hypnotist in the presence of the subject or are self-administered (self-hypnosis or autosuggestion.)

The words hypnosis and hypnotism both derive from the term “neuro-hypnotism” (nervous sleep) coined by the Scottish surgeon James Braid around 1841. Braid based his practice on the work of Franz Mesmer (Mesmerism or Animal Magnetism), but differed in his theory as to how the procedure worked.

Contrary to the popular misconception that hypnosis is an unconsciousness state similar to sleeping, research suggests that hypnotic subjects are fully awake and have a heighten focus of attention, with a corresponding decrease in their peripheral awareness. Subjects also show an increased response to suggestions.

In the first book on the subject, Neurypnology (1843), Braid described hypnotism as a state of physical relaxation accompanied and induced by mental concentration. Braid called this “abstraction.”