non-REM sleep

noun

ˈnän-ˌrem- 

variants or NREM sleep

ˈen-ˌrem- 

: a state of sleep that occurs regularly during a normal period of sleep with intervening periods of REM sleep and is characterized by delta wave brain activity, little dreaming, and a reduced level of autonomic physiological activity

Non-REM sleep is a quiet sleep state. The muscles are relaxed but maintain some tone, breathing is regular, the cerebral cortex generates high-voltage waves, and consumption of energy by the brain is minimal.

—Jerome M. Siegel

For most people the few dreams found in non-REM sleep tend to have a rather thought-like character. During REM sleep, on the other hand, dreams occur more frequently and usually have a perceptual vividness …

—Francis Crick et al.

NREM sleep … is crucial to memory retention, and to acquiring and refining our motor skills.

—David Kamp

compare rem sleep, slow-wave sleep

Examples of non-REM sleep in a Sentence

Recent Examples on the Web

Even moderate amounts disrupt non-REM sleep, which is the exact phase where the hormone surge happens. — Allison Palmer, Sacbee.com, 30 Apr. 2026

During non-REM sleep, the accelerator surges and the brake eases off. — Allison Palmer, Kansas City Star, 6 May 2026

Alcohol close to bedtime reliably disrupts non-REM sleep, even one or two drinks can cost you the deepest stages. — Allison Palmer, Miami Herald, 29 Apr. 2026

In mammals, this rhythm is strongly linked to non-REM sleep, the phase associated with dreams, physical restoration, and brain maintenance. — Rupendra Brahambhatt, Interesting Engineering, 24 Jan. 2026

Word History

First Known Use

1963, in the meaning defined above

Rhymes for non-REM sleep

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

Medical Definition

non-REM sleep

noun

-ˌrem- 

variants or NREM sleep

ˈen-ˌrem- 

: a state of sleep that occurs regularly during a normal period of sleep with intervening periods of REM sleep and is characterized by delta wave brain activity, little dreaming, and a reduced level of autonomic physiological activity

Non-REM sleep is a quiet sleep state. The muscles are relaxed but maintain some tone, breathing is regular, the cerebral cortex generates high-voltage waves, and consumption of energy by the brain is minimal.

—Jerome M. Siegel

NREM sleep … is crucial to memory retention, and to acquiring and refining our motor skills.

—David Kamp

called also orthodox sleep, S sleep, synchronized sleep

compare rem sleep, slow-wave sleep