lumens

noun pl. lumens or lumina

1. the basic unit used to measure the flow of light in the SI system, equal to the amount of light emitted through a solid angle of one steradian by a light source with the intensity of one candela (0.0015 watt): abbrev. lm
2. the bore of a hollow needle, catheter, etc.
3. Anat. the passage within a tubular organ