lumen
noun
[ ˈluːmɛn ]
• the SI unit of luminous flux, equal to the amount of light emitted per second in a unit solid angle of one steradian from a uniform source of one candela.
Origin:
late 19th century: from Latin, literally ‘light’.
lumen
noun
• the central cavity of a tubular or other hollow structure in an organism or cell.
• "the stomach empties food into the lumen of the small intestine"
Origin:
late 19th century: from Latin, literally ‘opening’.
