Hypertext Webster Gateway: "Lumina"
From Webster's Revised Unabridged Dictionary (1913) (web1913)
Lumen \Lu"men\, n.; pl. L. {Lumina}, E. {Lumens}. [L., light, an
opening for light.]
1. (Photom.)
(a) A unit of illumination, being the amount of
illumination of a unit area of spherical surface, due
to a light of unit intensity placed at the center of
the sphere.
(b) A unit of light flux, being the flux through one
square meter of surface the illumination of which is
uniform and of unit brightness.
2. (Biol.) An opening, space, or cavity, esp. a tubular
cavity; a vacuole.
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