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• rem
  rem

  noun

  the quantity of ionizing radiation whose biological effect is equal to that produced by one roentgen of x-rays.
• REM
  REM

  noun

  rapid eye movement.

rem

¹ American  

[rem] / rɛm /

noun

Nucleonics.

1. the quantity of ionizing radiation whose biological effect is equal to that produced by one roentgen of x-rays.

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REM ² American  

[rem] / rɛm /

noun

1. rapid eye movement.

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REM ¹ British  

abbreviation

1. rapid eye movement

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REM ² British  

/ rɛm /

acronym

1. roentgen equivalent man

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rem Scientific  

/ rĕm /

1. The amount of ionizing radiation required to produce the same biological effect as one rad of high-penetration x-rays. The rem has been replaced in most scientific contexts by the sievert.

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rem Cultural  

1. An acronym for r oentgen e quivalent m an. A unit of absorbed doses of radiation.

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Discover More

A normal medical x-ray delivers about 0.02 rem; a fatal dose of radiation is several thousand rem.

Etymology

Origin of rem¹

1945–50; r(oentgen) e(quivalent in) m(an)

Origin of REM²

First recorded in 1955–60

Example Sentences

See Examples For:

rem REM

NIOSH, trying to give Brogdon the benefit of the doubt, calculated the dose to his prostate at just above 35 rem.

From Slate ● Dec. 11, 2015

What is the dose in rem to the tumor, if the average γ energy per decay is 1.25 MeV?

From Textbooks ● Aug. 12, 2015

I would take 25 rem just to save my cat.

From Forbes ● May 19, 2013

In comparison, a dental X-ray delivers up to 15 millirems, or thousandaths of a rem, and a mammogram delivers a dose of about 70 millirems.

From Time ● Mar. 3, 2012

Harge rem ir Tibe was still close to us, overhearing, and I felt that he was meant to overhear.

From "The Left Hand of Darkness" by Ursula K. Le Guin

Current approaches to sleep problems, including medication and behavioral therapy, may cause side effects or may not directly address the underlying factors that interfere with REM sleep.

From Science Daily ● Aug. 7, 2026

Drug testing officials, rapping on the hotel doors of Pogacar and rival Jonas Vingegaard, in the middle of the night, deep REM time, reportedly with permission from a French judge.

From The Wall Street Journal ● Jul. 27, 2026

The anesthetized patients’ brains produced activity that shared similarities to being unconscious in a coma—as well as deep sleep, REM sleep and patterns unique to anesthesia.

From The Wall Street Journal ● Jun. 3, 2026

Disrupted REM sleep is commonly seen in conditions such as depression, anxiety, and Parkinson's disease.

From Science Daily ● Feb. 4, 2026

My mother is the only individual I know who can fall asleep instantly for two minutes—deep REM sleep, complete with snoring—only to be awakened instantly by certain select noises.

From "The Color of Water: A Black Man's Tribute to His White Mother" by James McBride