lumen
Americannoun
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lumens,
plural
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lumina
plural
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Optics. the unit of luminous flux, equal to the luminous flux emitted in a unit solid angle by a point source of one candle intensity. lm
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Anatomy. the canal, duct, or cavity of a tubular organ.
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Botany. (of a cell) the cavity that the cell walls enclose.
noun
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lm. the derived SI unit of luminous flux; the flux emitted in a solid angle of 1 steradian by a point source having a uniform intensity of 1 candela
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anatomy a passage, duct, or cavity in a tubular organ
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a cavity within a plant cell enclosed by the cell walls
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lumens
plural
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The central space within a tube-shaped body part or organ, such as a blood vessel or the intestine.
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The SI derived unit used to measure the amount of light passing through a given area per second. One lumen is equal to the luminous flux passing per unit solid angle from a light source with a strength of one candela.
Other Word Forms
Derived Forms
Inflected Forms
Nouns
Etymology
Origin of lumen
1870–75; < New Latin, special uses of Latin lūmen (stem lūmin- ) light, window
Explanation
The lumen is a unit of measurement for the brightness of light. If a light bulb is blindingly bright, it produces a lot of lumens. The lumen is a basic unit for measuring brightness, just as the gram is a basic unit for measuring mass. A typical light bulb in your home might produce about 1000 lumens. Lumen is related to the word luminous, which means “bright” or “radiant.”
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
Activated Ras mutant epithelial cells, which would normally be eliminated into the lumen, instead infiltrated diffusely into the tissue to form highly invasive cancerous tumors.
From Science Daily ● Nov. 22, 2023
Studies have reported that when activating mutants of "Ras" proteins are expressed in mammalian epithelial cells, they are pushed toward the lumen, excreted along with other bodily waste, and eliminated by competition.
From Science Daily ● Nov. 22, 2023
“If you break it down bio meaning life and lumen meaning light and so bioluminescence is really the all-encompassing term that refers to life that gives off light,” said Rouches.
From Seattle Times ● Aug. 28, 2023
IgA and other antibodies are secreted into the intestinal lumen.
From Textbooks ● Jun. 9, 2022
So we sat there for a couple hours talking to the screen together, navigating this invisible labyrinthine cave without a single lumen of light.
From "The Fault in Our Stars" by John Green
But many LED bulbs are installed with a much higher color temperature, near 4,000 Kelvins, which our brains interpret as harsh and bright, regardless of how many lumens they’re actually emitting.
From Los Angeles Times ● May 8, 2026
Langhelm said the LED lamps are pricey because they have a high intensity of “up to 55,000 lumens, compared to a household lamp of about 1,800 lumens,” and they are customized to fit each streetlight.
From Seattle Times ● Jan. 29, 2024
In March, Cree LED announced white LEDs offering 228 lumens per watt.
From BBC ● Dec. 18, 2023
These bulbs can create about 75 lumens with 1 watt of electricity.
From NewsForKids.net ● Aug. 17, 2023
Under this high-pressure system, mantle-burners yield as high as 500 lumens per cubic foot of gas per hour.
From Artificial Light Its Influence upon Civilization by Matthew Luckiesh
The lumina are filled with cellular detritus and are no longer bordered by a clear ring of sustentacular cytoplasm.
From Natural History of the Ornate Box Turtle, Terrapene ornata ornata Agassiz by John M. Legler
A quaint old rhyme says of the plant:— "Nobilis est ruta quia lumina reddit acuta."
From Herbal Simples Approved for Modern Uses of Cure by William Thomas Fernie
On page 40 appear the following lines:— Terribili squarlore Charon eni plurina mento Canities inculta jucet; staut lumina flaurina Nor is he happier in his quotations from Italian, or in his other displays of learning.
From The Atlantic Monthly, Volume 01, No. 03, January, 1858 by Various
Those lumina mundi believe that the people will forget their records.
From Diary from November 12, 1862, to October 18, 1863 by Adam G. de Gurowski, Count
The intima of these vessels was in places so swollen as to resemble cylindrical or spindle-shaped hyaline masses, and cause narrowing of the lumina of the vessels in which this degeneration occurred.
From A System of Practical Medicine by American Authors, Vol. I Volume 1: Pathology and General Diseases by Various
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