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Definition of: lumen
(l′mən) noun plural ·mens or ·mi·na (-mə·nə)
1. A passageway or opening.
2. Biol. The inner cavity of a cell or tubular organ, as a gland.
3. Physics A unit for measuring luminous flux, equal to the flow through a steradian from a uniform point source of one international candle. [<L, light]
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