This noun describes the radiance or brightness that emanates from a luminous source. It emphasizes the outshining of light rather than the source itself—the effulgence rather than the luminary. Hebrews 1:3 uses it in a profound Christological statement: the Son is 'the radiance of God's glory'—the brightness that beams forth from the Father. Like sunlight proceeding from the sun, the Son radiates the Father's glory while remaining distinct in person yet identical in divine nature. This single word carries enormous theological weight about Christ's relation to the Father.