Defects in Solids. Why Do Defects Form?. Some Thermodynamics Ideas. Point Defects. The Statistics of Point Defects. Line Defects—Dislocations. Edge Dislocations. Screw Dislocations. Burger’s Vector and the Burger Circuit. Dislocation Motion. Planar Defects. Grain Boundaries. Twin Boundaries. Three-Dimensional Defects