## Wikipedia - Absorptance (en) absorptance, $$\alpha$$

https://doi.org/10.1351/goldbook.A00035
Ratio of the absorbed to the incident @[email protected] Also called @[email protected] When $$\alpha \leq 1$$, $$\alpha \approx A_{\text{e}}$$, where $$A_{\text{e}}$$ is the Napierian @[email protected]
Source:
Green Book, 2nd ed., p. 32 [Terms] [Book]