What does sleep mean?
Sleep is the periodic state of rest in which a person or animal has reduced awareness, little responsiveness to outside stimuli, and generally relaxed muscles. As a verb, it describes entering this state, spending time in it, or being asleep. The expression 'a good night's sleep' refers to a long and restorative period of rest, while 'fall asleep' describes the transition into sleep. Sleep is essential for health and plays an important role in memory, learning, emotional regulation, and physical recovery. Although sleep is usually treated as a single, familiar activity, its rhythms and requirements vary with age, health, and individual circumstances. The word can also be used figuratively for being unaware of surrounding events, as in someone who slept through an announcement.
A state or period of rest in which a person or animal has reduced consciousness and responsiveness.
"Lack of sleep left him unable to concentrate at work."
Sleep can refer generally to the activity or to a particular period of it. 'A sleep' is less common in modern English than 'a night's sleep' or 'some sleep.'
To rest in a state of reduced consciousness and responsiveness, or to spend time sleeping.
"The children slept at their grandmother's house."
The verb is standard in everyday English. In figurative use, it can mean to fail to notice or respond to something happening.
Usually used for individual periods of sleep; the plural is not needed for the activity in general.
"The new parents managed only a few short sleeps each night."
Sleep is one of the few human experiences that is both utterly ordinary and still mysterious: the brain remains active while the body rests, helping consolidate memory and restore the body.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does sleep come from?
The English word descends from Old English slǣpan, meaning 'to rest' or 'sleep', and the related noun slǣp. These forms trace to Proto-Germanic *slēpaną and *slēps, meaning 'sleep' or 'rest'. English cognates include German schlafen and Dutch slapen, which preserve the same Germanic root. The modern pronunciation with /iː/ reflects the regular development of the Old English long vowel.
Related word forms
How sleep is actually used
The noun is standard in everyday English and is neutral in register. As a verb, sleep is also neutral, though phrases such as 'sleep like a log' and 'sleep on it' are more informal.
Easily confused with sleep
Sleep is the general state or act of sleeping, while slumber often suggests a prolonged or especially peaceful sleep and is more literary in tone.
A nap is a short period of sleep, usually taken during the day, whereas sleep can refer to any period of sleeping, including a full night's rest.