glue, gelatin-like adhesive substance extracted from animal tissue, particularly hides and bones, or from fish, casein (milk solids), or vegetables. Glue was used as early as 3000 bce in wooden furniture construction in Egypt.
Synthetic resin adhesives such as the epoxies are replacing glue for many uses, but glue is still widely used as an adhesive in woodworking, in the manufacture of such abrasives as sandpaper, and as a colloid in industrial processes—e.g., the recovery of solid particles suspended in a liquid.