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
   "The LED bulb produces 800 lumens";
   - 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