A colloidal dispersion is a soft material consisting of solid particles spread throughout a fluid. According to Jones (p. 49), colloidal particles must have dimensions on the order of 10<math>\mu</math>m or smaller.
Witten (p. 113) distinguishes between colloids (solid particles in liquid), emulsions (liquid drops in another liquid), and foams (bubbles of gas in a liquid), Jones (p. 1) includes emulsions in his definition of colloids.
Jones, Richard A. L., "Soft Condensed Matter," Oxford University Press Inc., New York (2002).
Witten, Thomas A., "Structured Fluids: Polymers, Colloids, Surfactants," Oxford University Press Inc., New York (2004).