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[loo-muh n] /ˈlu mən/
noun, plural lumens, lumina
[loo-muh-nuh] /ˈlu mə nə/ (Show IPA)
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.
Abbreviation: lm.
Anatomy. the canal, duct, or cavity of a tubular organ.
Botany. (of a cell) the cavity that the cell walls enclose.
Origin of lumen
1870-75; < New Latin, special uses of Latin lūmen (stem lūmin-) light, window Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for lumen
Historical Examples
  • That reminds me, I'd better arrange a debate on immigration for the lumen.

    Ramsey Milholland Booth Tarkington
  • "She made a splendid impression on the lumen," Colburn went on.

    Ramsey Milholland Booth Tarkington
  • If the lumen of the tube is as fine as a hair, a considerable rise can be observed.

    Natural Philosophy Wilhelm Ostwald
  • Just one more word, lumen, before we conclude this interview.

    Lumen Camille Flammarion
  • Dear lumen, I do not half understand this new effect of the laws of light.

    Lumen Camille Flammarion
  • The internal coat was plicated, as if too large for the lumen.

  • If lumen had been to blame for the quarrel, he paid a fearful penalty.

    A Busy Year at the Old Squire's

    Charles Asbury Stephens
  • Reflection and study had already inclined me, lumen, to believe in the plurality of the existences of the soul.

    Lumen Camille Flammarion
  • To use the words of Bacon: lumen siccum et aridum ingenia madida offendit et torret.

    Problems in Greek history John Pentland Mahaffy
  • A lambert is "the brightness of a perfectly diffusing surface radiating or reflecting one lumen per square cm."

    The Nature of Animal Light E. Newton Harvey
British Dictionary definitions for lumen


noun (pl) -mens, -mina (-mɪnə)
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 lm
(anatomy) a passage, duct, or cavity in a tubular organ
a cavity within a plant cell enclosed by the cell walls
Derived Forms
lumenal, luminal, adjective
Word Origin
C19: New Latin, from Latin: light, aperture
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
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Word Origin and History for lumen

unit of luminosity, 1897, coined 1894 by French physicist André-Eugène Blondel (1863-1938) from Latin lumen "light," related to lucere "to shine" (see light (n.)).

Online Etymology Dictionary, © 2010 Douglas Harper
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lumen in Medicine

lumen lu·men (lōō'mən)
n. pl. lumens or lu·mi·na (-mə-nə)

  1. The inner open space or cavity of a tubular organ, as of a blood vessel.

  2. The unit of luminous flux in the International System of Units, that is equal to the amount of light given out through a solid angle by a source of one candela intensity radiating equally in all directions.

lu'men·al or lu'min·al adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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lumen in Science
Plural lumens or lumina
  1. The central space within a tube-shaped body part or organ, such as a blood vessel or the intestine.

  2. 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.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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