absorptance
/abˈzɔːpt(ə)ns/ /abˈsɔːpt(ə)ns/Physics
noun
A measure of the degree to which a substance or object absorbs radiation incident on it, equal to the ratio of the absorbed to the incident flux.
Origin
1920s. From classical Latin absorpt-, past participial stem of absorbēre absorb + -ance, probably after reflectance.