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La Le Li Lo Lu Ly
Luc Lum Lun Lus Lut

Lumen

 /ˈlo͞omən/

Noun, pl. lumens

(Physics)
1. In the International System of Units, the derived unit of luminous flux; the light that is emitted in a solid angle of one steradian from a source of one candela. (wiktionary.org)

2. 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

Symbol: lm

Noun, pl. lumina

(Anatomy)
The cavity or channel within a tube or tubular organ. (wiktionary.org)

(Botany)
The cavity bounded by a plant cell wall. (wiktionary.org)

(Medicine)
The bore of a tube such as a hollow needle or catheter. (wiktionary.org)

Word origin: From Latin lumen “light,” related to lucere “to shine”

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