WAestivation
WCortisol awakening response
WDelayed sleep phase disorder
WHibernation
WK-complex
WLucid dream
WDream
WNight hag
WPineal gland
WRapid eye movement sleep
WRetinohypothalamic tract
WSecond wind (sleep)
WSleep and creativity
WSleep and emotions
WSleep apnea
WSleep cycle
WSleep debt
WSleep in fish
WSleep in non-human animals
WSleep medicine
WSleep paralysis
WSlow-wave sleep
WSuprachiasmatic nucleus
WUltradian rhythm
WUnihemispheric slow-wave sleep
WYawn