attenuation coefficient

Analogous to absorption coefficient but taking into account also the effects due to scattering and luminescence. It was formerly called extinction coefficient.
Green Book, 2nd ed., p. 32
See also:
Orange Book, p. 212
PAC, 1996, 68, 957 (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 963