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

By nine months, the results showed even less REM sleep, pointing toward a progressive decline. —Angelica Stabile, FOXNews.com, 7 Apr. 2026

REM sleep plays a vital role in memory consolidation, emotional regulation and cognitive function. —Allison Palmer, Miami Herald, 7 Apr. 2026

Nineteen fewer minutes of REM sleep is significant. —Allison Palmer, Kansas City Star, 7 Apr. 2026

Researchers cautioned that all-night broadband noise may be especially harmful to children, who cycle through significantly more REM sleep than adults. —Allison Palmer, Fort Worth Star-Telegram, 7 Apr. 2026

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