Hypnagogia is the experience of the transitional state from wakefulness to sleep: the hypnagogic state of consciousness, during the onset of sleep. In opposition, hypnopompia denotes the onset of wakefulness. The related words from the Greek are agōgos "leading", "inducing", pompe "act of sending", and hypnos "sleep".Mental phenomena that occur during this "threshold consciousness" phase include lucid dreaming, hallucinations, and sleep paralysis.