noun \ˈslēp\

: the natural state of rest during which your eyes are closed and you become unconscious

: a period of sleep especially of a particular kind

: the dry substance that sometimes forms in the corners of your eyes while you are sleeping

Full Definition of SLEEP

:  the natural periodic suspension of consciousness during which the powers of the body are restored — compare REM sleep, slow-wave sleep
:  a state resembling sleep: as
a :  a state of torpid inactivity
b :  death <put a pet cat to sleep>; also :  trance, coma
c :  the closing of leaves or petals especially at night
d :  a state marked by a diminution of feeling followed by tingling <my foot's gone to sleep>
e :  the state of an animal during hibernation
a :  a period spent sleeping
b :  night
c :  a day's journey
:  crusty matter present in the corner of an eye upon awakening
sleep·like \-ˌlīk\ adjective

Examples of SLEEP

  1. I just need to get some sleep.
  2. How much sleep did you get last night?
  3. Her roommate talks in her sleep.
  4. The noise woke her from a deep sleep.
  5. He woke up and rubbed the sleep out of his eyes.

Origin of SLEEP

Middle English slepe, from Old English slǣp; akin to Old High German slāf sleep and perhaps to Latin labi to slip, slide
First Known Use: before 12th century

Other Physiology Terms

eructation, flux, gustatory, menarche, myopia, senescence, torpor



: to rest your mind and body by closing your eyes and becoming unconscious

: to have enough space for (a specified number of people) to sleep in it

slept \ˈslept\ sleep·ing

Full Definition of SLEEP

intransitive verb
:  to rest in a state of sleep
:  to be in a state (as of quiescence or death) resembling sleep
:  to have sexual relations —usually used with with
transitive verb
:  to be slumbering in <slept the sleep of the dead>
:  to get rid of or spend in or by sleep <sleep away the hours> <sleep off a headache>
:  to provide sleeping accommodations for <the boat sleeps six>

Examples of SLEEP

  1. I couldn't sleep last night. I was awake all night long.
  2. I usually try to sleep for at least eight hours every night.
  3. Did you sleep soundly last night?
  4. We were sleeping peacefully when a sudden loud noise woke us up.
  5. I can never sleep on airplanes.
  6. The tent sleeps five adults.

First Known Use of SLEEP

before 12th century


noun    (Concise Encyclopedia)

Natural periodic suspension of consciousness during which the powers of the body are restored. Humans normally sleep at night, whereas nocturnal species sleep during the day. Adult humans sleep between six and nine hours per night, though increasing numbers of people sleep less than six hours. Sleep is divided into two main types: REM (rapid-eye-movement) and NREM (non-REM), each of which recurs cyclically several times during a normal period of sleep. REM sleep is characterized by increased neuronal activity of the forebrain and midbrain, by depressed muscle tone, and by dreaming (see dream), rapid eye movements, and vascular congestion of the sex organs. NREM sleep is divided into stages, the last of which is the deep, restorative, quiet sleep commonly associated with “a good night's rest.” See also insomnia; narcolepsy.


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