General relations for entrainment and minimum fluidization are derived from Stokes' law and Newton's law using Ergun's idea that laminar and turbulent Row effects are always present. Numerical criteria are developed to discriminate different classes of fluidized powders mainly on the basis of critical values for the ratio between laminar and turbulent Row effects at the two benchmark situations of fluidization. The resulting critical Archimedes numbers are checked with literature information. Application to fluidization with ambient air allows a comparison of this general classification of any fluid-solid combination with Geldart's diagram and with Molerus' classification diagram.