1884; Germancoined by German physicist Eilhard Wiedemann (1852-1928) from Latin lumen (genitive luminis) "light" (from suffixed form of PIE root *leuk- "light, brightness")

emitting light that is not caused by incandescence and that occurs at a temperature below that of incandescent bodies:

The stained glass windows in the foyer were luminescent as the sun went down.