This document summarizes a lecture on particle size analysis. It discusses: 1) The importance of characterizing particle size distribution in industrial processes and defining an average size. 2) How particle size is conventionally measured using different units depending on size range, from inches/millimeters for coarse particles to micrometers/nanometers for fine particles. 3) Common particle size ranges termed very coarse through very fine and examples like wood chips, urea, and carbon black. 4) How screen analysis works by stacking sieves from coarsest to finest and measuring the material retained on each to determine the particle size distribution.