[loo-muh n]
noun, plural lu·mens, lu·mi·na [loo-muh-nuh] /ˈlu mə nə/.
  1. 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
  2. Anatomy. the canal, duct, or cavity of a tubular organ.
  3. 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 Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for lumina


noun plural -mens or -mina (-mɪnə)
  1. 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 candelaSymbol: lm
  2. anatomy a passage, duct, or cavity in a tubular organ
  3. a cavity within a plant cell enclosed by the cell walls
Derived Formslumenal or luminal, adjective

Word Origin for lumen

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

Word Origin and History for lumina



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

lumina in Medicine


n. pl. lumens
  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, equal to the amount of light given out through a solid angle by a source of one candela intensity radiating equally in all directions.
Related formslumen•al null adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

lumina in Science


Plural lumens 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 © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.