Phenomenon of the emission, by matter, of electromagnetic radiation which for certain wavelengths or restricted regions of the spectrum is in excess of that due to the thermal radiation from the material at the same temperature. The radiation is characteristic of the particular material.
Note: In lighting this term is generally restricted to the emission of radiation in the visible or near visible spectrum.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
Celsius (previously Centigrade)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM