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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

The legal limit for radiation exposure in the workplace is 5 rem per year.

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

According to the government report, with each scan, the average passenger receives a dose of about 1.46 microrems, or millionths of a rem, the standard measure of a person’s radiation exposure.

From Time ● Mar. 3, 2012

“It takes the form of money—some of your own—Foreth rem ir Osboth sends it. I have it with me, at Mr. Shusgis’ house.

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

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

Basner also pointed out that children spend significantly more time in REM sleep than adults, which may make them especially sensitive to its disruption.

From Science Daily ● Feb. 4, 2026

Both deep sleep and REM sleep were significantly shorter, and participants spent an additional 15 minutes awake during the night.

From Science Daily ● Feb. 4, 2026

“People are saying ‘I know I only got 30 minutes of deep sleep and an hour of REM.

From The Wall Street Journal ● Dec. 29, 2025

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