The capacity of a material to absorb incident radiant energy. A special case of absorptance, it is a fundamental property of material that has a specular (optically smooth) surface and is sufficiently thick to be opaque. It may be further qualified as spectral absorptivity Absorptivity-emissivity ratio: The ratio of absorptivity of solar radiation to infrared emissivity of a material.
The capacity of a material to absorb incident radiant energy, measured as the ratio of the amount of radiant energy absorbed to the total amount incident on the material.
The ratio of absorbed radiation by an object to the absorbed radiation by a black body at the same wavelength and temperature.