## Wikipedia - Absorbance absorbance, $$A$$

https://doi.org/10.1351/goldbook.A00028
Logarithm of the ratio of incident to transmitted @R05046@ through a sample (excluding the effects on cell walls). Depending on the base of the logarithm a decadic and Napierian absorbance are used. Symbols: $$A$$, $$A_{10}$$, $$A_\text{e}$$. This quantity is sometimes called @E02293@, although the term @E02293@, better called @A00513@, is reserved for the quantity which takes into account the effects of @L03641@ and @S05487@ as well.
Source:
Green Book, 2nd ed., p. 32 [Terms] [Book]
See also:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2169 [Terms] [Paper]
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2226 [Terms] [Paper]