A night terror, also known as a sleep terror or pavor nocturnus, is a parasomnia disorder characterized by extreme terror and a temporary inability to regain full consciousness. The subject wakes abruptly from slow-wave sleep, with waking usually accompanied by gasping, moaning, or screaming while waking. It is often impossible to awaken the person fully because they are so concentrated on waking, and after the episode the subject normally settles back to sleep without waking. A night terror can rarely be recalled by the subject. They typically occur during non-rapid eye movement sleep.