noun, plural lu·ces [loo-seez] /ˈlu siz/, lux·es. Optics.

a unit of illumination, equivalent to 0.0929 foot-candle and equal to the illumination produced by luminous flux of one lumen falling perpendicularly on a surface one meter square. Symbol: lx

Origin of lux

1885–90; < Latin lūx light1
Also called meter-candle.


fiat lux

[fee-aht loo ks; English fee-aht luhks, fahy-uh t]


let there be light. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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British Dictionary definitions for lux



noun plural lux

the derived SI unit of illumination equal to a luminous flux of 1 lumen per square metre. 1 lux is equivalent to 0.0929 foot-candleSymbol: lx

Word Origin for lux

C19: from Latin: light




NZ informal to clean with a vacuum cleaner

Word Origin for lux

C20: from Electrolux, a vacuum-cleaner manufacturer


abbreviation for

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for lux

unit of illumination, 1889, from Latin lux "light" (see light (n.)).

Online Etymology Dictionary, © 2010 Douglas Harper

lux in Medicine



n. pl. lux•es

The International System unit of illumination, equal to one lumen per square meter.candle-meter meter-candle
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

lux in Science



Plural luxes luces (lōōsēz)

A SI derived unit of illuminance in photometry, equal to one lumen per square meter.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.