Lumen

• In anatomy, the lumen is the cavity or channel within a tube or tubular structure, such as the vascular lumen of a blood vessel, along which blood flows.

• In astronomy, 141 Lumen is the name of an asteroid discovered by the French astronomer Paul Henry in 1875.

• In physics, specifically photometry (optics), the lumen (symbol: lm) is the SI derived unit of luminous flux. It is the amount of light that falls on a unit area at unit distance from a source of one candela.