A
powder is a dry, bulk
solid composed of a large number of very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of
granular materials, although the terms
powder and
granular are sometimes used to distinguish separate classes of material. In particular,
powders refer to those granular materials that have the finer grain sizes, and that therefore have a greater tendency to form clumps when flowing.
Granulars refers to the coarser granular materials that do not tend to form clumps except when wet.