Sawdust is created by sawing, grinding, or sanding. It may be wood, metal, mineral, composite, or ceramic.

Wood sawdust is the debris created by sawing, grinding, or sanding wood. It is characterized by particles consisting of multiple cell fragments or fragments of single cells that are uniform in thickness, retain typical birefringence, and are terminated by jagged breaks across the longitudinal axis of the cell. Many of these particles look like wood flour, a commercial product used as a filler in plastics, resins, and other matrices.