Hypnosis can be defined as:
a special psychological state with certain physiological attributes, resembling sleep only superficially and marked by a functioning of the individual at a level of awareness other than the ordinary conscious state.
According to "state theory", it is a mental state, while, according to "non-state theory", it is imaginative role-enactment. Hypnosis is usually induced by a procedure known as a hypnotic induction, which is commonly composed of a long series of preliminary instructions and suggestions. Hypnotic suggestions may be delivered by a hypnotist in the presence of the subject, or may be self-administered ("self-suggestion" or "autosuggestion"). The use of hypnotism for therapeutic purposes is referred to as "hypnotherapy", while its use as a form of entertainment for an audience is known as "stage hypnosis".
The term “hypnosis” comes from the Greek word hypnos which means sleep. 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 that developed by Franz Mesmer and his followers ("Mesmerism" or "animal magnetism"), but differed in his theory as to how the procedure worked.
Contrary to a popular misconception—that hypnosis is a form of unconsciousness resembling sleep—contemporary research suggests that hypnotic subjects are fully awake and are focusing 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 ("abstraction"). In addition, psychiatric nurses in most medical facilities are allowed to administer hypnosis to patients in order to relieve symptoms such as anxiety, arousal, negative behaviors, uncontrollable behavior, and improve self-esteem and confidence only when they have been completely trained about their clinical side effects and while under supervision when administering it.