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

People awakened during REM sleep usually report dreams with visual images and storylike narratives.

—Lis Harris

called also paradoxical sleep, rapid eye movement sleep

compare slow-wave sleep, non-REM sleep

Examples of REM sleep in a Sentence

Recent Examples on the Web

These first signs, Pfeffer said, include constipation, a loss of smell and REM sleep behavior disorder, a condition in which people act out their dreams while sleeping. —Ian Randall, MSNBC Newsweek, 1 July 2025

The Index tracks a bunch of metrics, including sleep duration, sleep stages (light, deep, and REM sleep), heart rate, blood oxygen saturation, breathing variations, and skin temperature changes. —Abhimanyu Ghoshal, New Atlas, 19 June 2025

Summer barbecues and partying come with more alcohol, when disrupt REM sleep. —Jesse Pines, Forbes.com, 12 June 2025

Following deep sleep, REM sleep is the next critical phase of sleep cycles, characterized by more dreaming that’s also extra vivid and lifelike, and by faster heart rate and breathing. —Kristen Rogers, CNN Money, 8 June 2025

Word History

First Known Use

1963, in the meaning defined above

Rhymes for REM sleep

• asleep
• upkeep
• beep
• cheap
• creep
• deep
• heap
• jeep
• keep
• leap
• peep
• reap

Medical Definition

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

People awakened during REM sleep usually report dreams with visual images and storylike narratives.

—Lis Harris

called also desynchronized sleep, paradoxical sleep, rapid eye movement sleep

compare non-rem sleep