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Pronunciation: lu'men, -min-a, -menz


  1. The space in the interior of a hollow tubular structure (artery or intestine).
  2. The unit of luminous flux; the luminous flux emitted in a unit solid angle of 1 steradian by a uniform point source of light having a luminous intensity of 1 candela.
  3. The volume enclosed within the membranes of a mitochondrion or of the endoplasmic reticulum.
  4. The bore of a catheter or hollow needle.

[L. light, window]

Further information

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© Copyright 2018 Wolters Kluwer. All Rights Reserved. Review date: Sep 19, 2016.