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:
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
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
“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
These cells absorb material from the lumen of the digestive tract and prepare it for entry into the body through the circulatory and lymphatic systems.
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
The documents are highly sensitive to light, and the lumens of the overhead lamps are kept as low as candlelight to avoid risking degradation.
From Los Angeles Times ● Apr. 24, 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
Mr Scheidt notes that for warm-toned LEDs, the efficiency drops somewhat, but it's still possible to achieve around 160 lumens per watt for warm white luminaires, with a colour temperature of 2,700 kelvin.
From BBC ● Dec. 18, 2023
These bulbs can create about 75 lumens with 1 watt of electricity.
From NewsForKids.net ● Aug. 17, 2023
The best practice now deals with the total light output, which is expressed in lumens, and on this basis a consumption of one gallon of kerosene per hour would yield about 8000 lumens.
From Artificial Light Its Influence upon Civilization by Matthew Luckiesh
Branches of the stem bronchus in either lung are exposed, or their respective lumina presented, by manipulation of the lip of the bronchoscope, with movement of the head in the required direction.
From Bronchoscopy and Esophagoscopy A Manual of Peroral Endoscopy and Laryngeal Surgery by Chevalier Jackson
The gray light of the waning moon, sifting through the boughs, was the true lumina for reverie.
From The Mascot of Sweet Briar Gulch by F. Graham Cootes
In Merulius lacrymans Hartig has observed thin-walled hyphae with large lumina, the septa of which are perforated like those of sieve-tubes.
From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" by Various
Strictural lumina are much more apt to be concentric as approached from below because there has been no distortion by pressure dilatation due to stagnation of the food operating through a long period of time.
From Bronchoscopy and Esophagoscopy A Manual of Peroral Endoscopy and Laryngeal Surgery by Chevalier Jackson
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
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
