Nonluminous

Nonluminous is an adjective used to describe an object or body that does not emit light and therefore is not self-luminous. Such an object may be dark or merely visible because it reflects light from another source.

The term is commonly applied in astronomy to distinguish bodies like planets, moons, and most asteroids from luminous objects such as stars and nebulae, which produce light themselves. In this context, nonluminous bodies appear only through reflected illumination and can vary in brightness according to albedo and external lighting conditions.

In materials science and everyday language, nonluminous materials do not glow or emit visible light. They may still reflect or scatter light, and the description contrasts with luminous or luminescent materials that emit light either continuously or intermittently.

In biological contexts, nonluminous describes organisms that do not produce light, in contrast with bioluminescent species. The term highlights the absence of intrinsic light emission rather than the absence of visibility.

Etymology: from Latin non (not) + lumen (light). See also luminescence, illumination, reflectance.