REM sleep
noun
: a state of sleep that recurs cyclically with non-REM sleep several times during a normal period of sleep, is characterized especially by greatly depressed muscle tone, dreaming with vivid imagery, rapid eye movements, and increased neuronal activity in certain brain regions (such as the pons), and typically comprises up to 25% of time spent in sleep
REM sleep, it soon became apparent, occurs in intervals throughout the night, usually four to six times, each lasting from ten minutes to an hour.—
Martin Gardner
Martin GardnerPeople awakened during REM sleep usually report dreams with visual images and storylike narratives.—Lis Harris
Lis Harriscalled also paradoxical sleep, rapid eye movement sleep
compare slow-wave sleep, non-REM sleepExamples of REM sleep in a Sentence
Recent Examples on the Web
When people woke from REM sleep, their cortex woke up in the same way, but without the preceding slow wave.
—Yasemin Saplakoglu, Quanta Magazine, 17 Oct. 2025
The researchers also noticed that participants took 30 minutes longer to reach the REM sleep phase (i.e. the dream stage of sleep).
—Clarissa Brincat, Popular Science, 16 Oct. 2025
Outwardly, REM sleep looks like rest.
—Rachel Barr, Big Think, 20 Aug. 2025
According to a study from the Journal of Physiological Anthropology, heat exposure increases wakefulness and decreases time spent in deep sleep and REM sleep.
—Molly Higgins, Wired News, 10 Aug. 2025
See All Example Sentences for REM sleep
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Yasemin Saplakoglu, Quanta Magazine, 17 Oct. 2025
The researchers also noticed that participants took 30 minutes longer to reach the REM sleep phase (i.e. the dream stage of sleep).
—Clarissa Brincat, Popular Science, 16 Oct. 2025
Outwardly, REM sleep looks like rest.
—Rachel Barr, Big Think, 20 Aug. 2025
According to a study from the Journal of Physiological Anthropology, heat exposure increases wakefulness and decreases time spent in deep sleep and REM sleep.
—Molly Higgins, Wired News, 10 Aug. 2025
See All Example Sentences for REM sleep
Cite this Entry
“REM sleep.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/REM%20sleep. Accessed 28 Oct. 2025.
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REM sleep
noun
: a state of sleep that recurs cyclically with non-REM sleep several times during a normal period of sleep, is characterized especially by greatly depressed muscle tone, dreaming with vivid imagery, rapid eye movements, and increased neuronal activity in certain brain regions (as the pons), and typically comprises up to 25% of time spent in sleep
REM sleep, it soon became apparent, occurs in intervals throughout the night, usually four to six times, each lasting from ten minutes to an hour.—Martin Gardner
Martin GardnerPeople awakened during REM sleep usually report dreams with visual images and storylike narratives.—Lis Harris
Lis Harriscalled also desynchronized sleep, paradoxical sleep, rapid eye movement sleep
compare non-rem sleepLove words? Need even more definitions?
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