Pronunciation: lū′men, -min-ă, -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.
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