lumen

/ˈlumən/

Other forms: lumina; lumens

The lumen is a unit of measurement for the brightness of light. If a light bulb is blindingly bright, it produces a lot of lumens.

The lumen is a basic unit for measuring brightness, just as the gram is a basic unit for measuring mass. A typical light bulb in your home might produce about 1000 lumens. Lumen is related to the word luminous, which means “bright” or “radiant.”

Definitions of lumen

1. noun

   a cavity or passage in a tubular organ
   “the lumen of the intestine”

   type of:

   bodily cavity, cavity, cavum

   (anatomy) a natural hollow or sinus within the body
2. noun

   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
   synonyms: lm

   type of:

   luminous flux unit

   a measure of luminous flux per unit area