Hypnotherapy

Hypnotherapy is a therapy that is undertaken with a subject in hypnosis.

The word "hypnosis" (from the Greek hypnos, "sleep") is an abbreviation of James Braid's (1841) term "neuro-hypnotism", meaning "sleep of the nervous system".

A person who is hypnotized displays certain unusual characteristics and propensities, compared with a non-hypnotized subject, most notably hyper-suggestibility, which some authorities have considered a sine qua non of hypnosis.

Clark L. Hull, probably the first major empirical researcher in the field, wrote

If a subject after submitting to the hypnotic procedure shows no genuine increase in susceptibility to any suggestions whatever, there seems no point in calling him hypnotised...