means The quality of giving off light, warmth, or visible joy — whether from a star, a fire, or a face.

from From Latin radiare, 'to emit beams,' built on radius, meaning a 'ray,' 'rod,' or 'spoke of a wheel.' That same radius gives us radio, radiation, and the geometry-class radius — all of them branching out from a single center, the way light spreads from its source. Radiance reached English through Latin's radiantia, the state of beaming.