The Webster's New International Dictionary defines hypnosis as "the induction of a state resembling sleep or somnambulism, which is called hypnosis or hypnotic sleep; also loosely - the induced state of hypnosis."
The word hypnosis is derived from the Greek word hypnos, meaning sleep. Hypnotism is often presumed to make someone go under a state of reduced consciousness while the person remains awake. The general behavior of those under hypnosis are being extremely positive to suggestions, and achieving a high level of relaxation. Daydreaming is another activity likened to hypnotism, wherein a person looks oblivious to his surroundings yet experiencing heightened imagination - depending on how light the trance is.