n]
. | 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. Abbreviation: lm |
| 2. | Anatomy. the canal, duct, or cavity of a tubular organ. |
| 3. | Botany. (of a cell) the cavity that the cell walls enclose. |

lu·men (lōō'mən) n. pl. lu·mens or lu·mi·na (-mə-nə)
[Latin lūmen, an opening, light; see leuk- in Indo-European roots.] lu'men·al, lu'min·al adj. |
lumen lu·men (l&oomacr;'mən)
n. pl. lumens or lu·mi·na (-mə-nə)
The inner open space or cavity of a tubular organ, as of a blood vessel.
The unit of luminous flux in the International System of Units, that is equal to the amount of light given out through a solid angle by a source of one candela intensity radiating equally in all directions.