emissiv

Emissiv is a term used in physics, engineering and graphics to describe a property of a surface or object that emits light or other electromagnetic radiation. It covers thermal emission produced by an object's temperature as well as luminescent emission arising from electronic transitions, phosphors, or other internal processes. In English, the standard adjective is emissive; emissiv appears in several European languages such as Norwegian and Swedish.

In radiometry and heat transfer, emissivity (symbol ε) characterizes how effectively a surface radiates compared with a perfect black body at the same temperature. Emissivity values range from 0 to 1 and may depend on wavelength and viewing angle. The radiant power emitted by a surface is proportional to its emissivity and to the black-body emission at that temperature.

In computer graphics, an emissive material is one that produces light on its own. Emission adds to scene illumination and can be used to model light sources or self-luminous objects. In display technology, emissive displays such as OLED panels generate light directly rather than relying on reflected light.

In astronomy and spectroscopy, sources that emit characteristic radiation are described as emissive; emission nebulae, for example, glow by radiating light emitted by excited gas. Overall, the term emphasizes the act of emission rather than reflection or transmission, and its precise meaning depends on the scientific context.