The term "hypnosis" is derived from the Greek word hypnos , meaning "sleep." Hypnotherapists typically use exercises that bring about deep relaxation and an altered state of consciousness, also known as a trance. Many people routinely experience a trance-like state while they are watching television or sitting at a red light. A person in a trance or deeply focused state is unusually responsive to an idea or image, but this does not mean that a hypnotist can control his or her mind and free will. On the contrary, hypnosis can actually teach people how to master their own states of awareness. By doing so they can affect their own bodily functions and psychological responses.