Absorptance and Coefficient

Absorptance noun - A measure of the rate of decrease in the intensity of electromagnetic radiation (as light) as it passes through a given substance; the fraction of incident radiant energy absorbed per unit mass or thickness of an absorber.

Coefficient and absorptance are semantically related. In some cases you can use "Coefficient" instead a noun "Absorptance".

Coefficient noun - A constant number that serves as a measure of some property or characteristic.

Absorptance and coefficient are semantically related. Sometimes you can replace term "Absorptance" with "Coefficient", this nouns are similar.