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 (although whilst in a trance state patients cannot be made to do anything that is against their moral code).
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…
Hypnotherapy is often applied in order to modify a subject’s behavior, emotional content, and attitudes, as well as a wide range of conditions including dysfunctional habits, anxiety, stress-related illness, pain management, and personal development.