LUMEN

n. unit for measuring the rate at which light is transmitted (Optics); cavity, hollow space (Anatomy, Botany)

Lumen can mean:Lumen (unit), the SI unit of luminous fluxLumen (anatomy), the cavity or channel within a tubular structureThylakoid lumen, the inner membrane space of the chloroplast141 Lumen, an asteroid discovered by the French astronomer Paul Henry in 1875Lumen (band), Russian rock/metal band
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Lumen /lu·men/ pl. lu´mina [L.] 1. the cavity or channel within a tube or tubular organ. 2. the SI unit of luminous flux ; it is the light emitted [more]Lumen - Community and Resources

Noun
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
(synonym) lm
(hypernym) luminous flux unit
2. a cavity or passage in a tubular organ; "the lumen of the intestine"
(hypernym) cavity, bodily cavity, cavum

n. (Physics) lumen, unit of light; cavity; (Botany) cellular cavity