What term is used to describe brightness or splendor?

The term "effulgence" specifically conveys a sense of shining brightness or brilliance that is particularly intense and radiant. It often implies a richness and a splendor that goes beyond mere brightness, suggesting an overflowing light or a brilliant radiance. This aligns well with the question asking for a term that embodies brightness or splendor, as "effulgence" can evoke imagery of a powerful light source radiating outward.

While "radiance," "luminescence," and "brilliance" also refer to aspects of brightness, they can have slightly different connotations or usages. "Radiance" often refers to the quality or state of being radiant, "luminescence" pertains more specifically to light emitted by a substance that is not caused by heat, and "brilliance" describes an intense brightness but may not encapsulate the same sense of splendor that "effulgence" carries. This makes "effulgence" the most fitting choice in this context.