Directly related to sleep:
* Hypnosis: A state of heightened suggestibility and relaxation induced by a hypnotist.
* Hypnotic: Relating to hypnosis or having the power to induce sleep.
* Hypnotism: The practice of inducing hypnosis.
* Hypnotist: A person who practices hypnotism.
* Hypnopath: A person who suffers from sleep disorders.
* Hypnogenic: Tending to induce sleep.
* Hypnopedia: The theory of learning during sleep.
Related to sleep but with different meanings:
* Hypnology: The scientific study of sleep.
* Hypnoscope: An instrument used to study sleep patterns.
* Hypnosurgery: Surgery performed on patients under hypnosis.
* Hypnosynthesis: The creation of new ideas or images while under hypnosis.
Figurative uses:
* Hypnospace: A fictional space or dimension where sleep is paramount.
* Hypnotically: In a way that is hypnotic or mesmerizing.
It's worth noting that some of these words are less common than others.