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Noun: lumen (lumens,lumina)  loo-mun
  1. A unit of luminous flux equal to the amount of light given out through a solid angle of 1 steradian by a point source of 1 candela intensity radiating uniformly in all directions
    - lm
  2. A cavity or passage in a tubular organ
    "the lumen of the intestine"

Derived forms: lumens, lumina

Type of: bodily cavity, cavity, cavum, luminous flux unit

Encyclopedia: Lumen