text: Note: Where a given letter is used in both capital and lower case form (,  and  ,&thinsp;) the capital letter refers to the macroscopic observable and the lower case letter to the corresponding variable for an individual particle or layer of the material.  Greek symbols are used for properties of a single particle.
  :  – absorption fraction of a single layer
  :  – remission fraction of a single layer
  :  – transmission fraction of a single layer
  : ,  ,   – the absorption, remission, and transmission fractions for a sample composed of  layers
  :  – absorption fraction of a particle
  :  – back-scattering from a particle
  :  – isotropic scattering from a particle
  :  –  absorption coefficient defined as the fraction of incident light absorbed by a very thin layer divided by the thickness of that layer
  :  –  scattering coefficient defined as the fraction of incident light scattered by a very thin layer divided by the thickness of that layer