IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S. J. Chalk.
IUPAC, Compendium of Macromolecular Nomenclature, The Purple Book, 1st ed., p. 66
Turbidity is an optical quality that is the apparent absorbance of the incident radiation due to scattering. For small particles, direct proportionality exists between turbidity and the Rayleigh ratio. [IUPAC]