emissivity

emis·siv·i·ty

noun \ˌem-ə-ˈsiv-ət-ē, ˌē-ˌmis-ˈiv-\

plural emis·siv·i·ties

Definition of EMISSIVITY

: the relative power of a surface to emit heat by radiation : the ratio of the radiant energy emitted by a surface to that emitted by a blackbody at the same temperature