lu·​men | \ ˈlü-mən How to pronounce lumen (audio) \
plural lumens also lumina\ ˈlü-​mə-​nə How to pronounce lumina (audio) \

Definition of lumen

1 : the cavity of a tubular organ or part the lumen of a blood vessel
2 : the bore of a tube (as of a hollow needle or catheter)
3 : a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candle intensity

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Other Words from lumen

luminal or less commonly lumenal \ ˈlü-​mə-​nᵊl How to pronounce lumenal (audio) \ adjective

Did You Know?

There are two common units for measuring light, the candela and the lumen. Both are recognized as standard international units, which also include the second (for time), the kilogram (for weight), and the meter (for length). The candela is a measure of intensity; an ordinary candle gives off light with the intensity of about one candela. The lumen is a measure of "luminous flux;" a standard 100-watt lightbulb gives off 1500–1700 lumens. Luminous flux indicates how much light is actually perceived by the human eye. Technologies vary in how efficiently they turn electricity into light; halogen lights produce about 12 lumens per watt, ordinary incandescent lightbulbs produce about 15 lumens per watt, and compact fluorescent bulbs produce about 50 lumens per watt.

Examples of lumen in a Sentence

Recent Examples on the Web

For backup, Maglite’s compact Mag-Tac CR123 ($83) throws 310 lumens a whopping 600 feet, has a power saving mode, and clips onto your belt. Nick Davidson, Outside Online, "The Ultimate DIY Bug-Out Bag," 27 June 2018 Different bulbs require different wattage, but Mr. Conway cited 100 lumens per watt as a common level of efficiency, so that 1,600-lumen bulb burns a mere 16 watts of power. Kathryn O’shea-evans, WSJ, "Goodbye, Showy Chandeliers. Hello, Low-Key Lighting That Transforms Rooms," 25 Jan. 2019 The technology of the structure’s core–made from proprietary LED backlighting and Swarovski’s proprietary active panel technology–paired with the crystals to emit over 100,000 lumens that can be seen from all angles. Lucia Tonelli, ELLE Decor, "How Architect Daniel Libeskind Redesigned the Rockefeller Center Christmas Tree Star," 15 Nov. 2018 The sleek DayBlazer 1100 pumps out 1,100 lumens up front, while its partner’s three LEDs pack a 125-lumen punch with 270 degrees of visibility. Nick Davidson, Outside Online, "8 Pieces of Bike Gear to Keep You Safe on Your Commute," 23 May 2018 Too many lumens up the coast in Oakland, with that juggernaut named the Warriors. Bryce Miller,, "Memo to Luke Walton: Here's comes LeBron ... and all that comes with it," 2 July 2018 Their packaging is all about the numbers: wattage, lumens, Kelvin, lifetime hours of operation, annual energy costs. Adam Snitzer, miamiherald, "His purchase of lightbulbs was sealed with a K.I.S.S. | Miami Herald," 11 May 2018 Civil twilight provides enough lumens to read a book outside, pull weeds in your garden or anticipate bumps on a path of sodden wood chips. Ned Rozell, Anchorage Daily News, "What it’s like to run circles for 24 hours around the land of no night," 9 June 2018 Unlike, say, a powder room, most master baths do have windows that let in natural life, but designers can sometimes do more to up the lumens. Richard A. Marini, San Antonio Express-News, "Here are some of San Antonio’s most beautiful master bathrooms," 25 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'lumen.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of lumen

1873, in the meaning defined at sense 1

History and Etymology for lumen

New Latin lumin-, lumen, from Latin, light, air shaft, opening

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Dictionary Entries near lumen






lum hat


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Time Traveler for lumen

The first known use of lumen was in 1873

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More Definitions for lumen


lu·​men | \ ˈlü-mən How to pronounce lumen (audio) \
plural lumina\ -​mə-​nə How to pronounce lumina (audio) \ or lumens

Medical Definition of lumen

1 : the cavity of a tubular organ or part the lumen of a blood vessel
2 : the bore of a tube (as of a hollow needle or catheter)
3 : a unit of luminous flux equal to the light emitted in a steradian by a uniform point source of one candle intensity

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More from Merriam-Webster on lumen

Rhyming Dictionary: Words that rhyme with lumen

Britannica English: Translation of lumen for Arabic Speakers Encyclopedia article about lumen

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