Difference between the scattering intensity for a dilute solution or a dilute dispersion and that for the pure solvent or the dispersion medium at the same scattering angle.
Source: PAC, 2015, 87, 71. (Definitions of terms relating to individual macromolecules, macromolecular assemblies, polymer solutions, and amorphous bulk polymers (IUPAC Recommendations 2014)) on page 109 [Terms] [Paper]