/looh"meuhn/ , n. , pl. lumens, lumina /-meuh neuh/ .
1. Optics. the unit of luminous flux, equal to the luminous flux emitted in a unit solid angle by a point source of one candle intensity. Abbr.: lm
2. Anat. the canal, duct, or cavity of a tubular organ.
3. Bot. (of a cell) the cavity that the cell walls enclose.
[ 1870-75; lumen (s. lumin- ) light, window ]