Sleep is a natural state of bodily rest observed throughout the animal kingdom. It is common to all mammals and birds, and is also seen in many reptiles, amphibians and fish.

A sleep disorder (somnipathy) is a medical disorder of the sleep patterns of a person or animal. Some sleep disorders are serious enough to interfere with normal physical, mental ...

verb (used without object) 1. to take the rest afforded by a suspension of voluntary bodily functions and the natural suspension, complete or partial, of consciousness; cease ...

Fact sheet on normal sleep and sleep disorders developed by the National Institute of Neurological Disorders and Stroke (NINDS).

sleepfoundation.org is dedicated to improving the quality of life for Americans who suffer from sleep problems and disorders such as insomnia, sleep apnea and restless legs ...