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:
Instead of being eliminated to the lumen, they infiltrate into the tissue, producing high-grade cancer cells.
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
While most kitchen lighting is built in, it’s possible to bring a few extra lumens to dark corners, and an extra dash of style, with plug-in lamps.
From Seattle Times ● Jan. 8, 2024
In March, Cree LED announced white LEDs offering 228 lumens per watt.
From BBC ● Dec. 18, 2023
Most incandescent bulbs can only create about 15 lumens with 1 watt, so they don’t meet the guidelines.
From NewsForKids.net ● Aug. 17, 2023
This lamp, known as the magnetite-arc, has a luminous efficiency of about 20 lumens per watt with a clear glass globe.
From Artificial Light Its Influence upon Civilization by Matthew Luckiesh
Celsius and Linnæus were complimented with the title of lumina academiæ, on account of their great learning and reputation.
From Lives of Eminent Zoologists, from Aristotle to Linnæus with Introductory remarks on the Study of Natural History by William MacGillivray
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
These flowers were the flaventia lumina Calthoe of Columella, described by Shakespeare in the Winter's Tale.
From Herbal Simples Approved for Modern Uses of Cure by William Thomas Fernie
In other cases Fungi, and even Bacteria, have been found to have made their way into the principal vessels, the lumina of which they stop up, thus reducing the transpiration current.
From Disease in Plants by H. Marshall Ward
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
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.
