Line imperfections are called dislocations. A linear disturbance, i.e. one dimensional imperfections in the
geometrical sense of the atomic arrangement, which can very easily occur on the slip plane through the
crystal, is known as dislocation. The most important kinds of linear defects are edge and screw dislocation.
Both these types are formed in the process of their deformation. Both these defects are the most striking
imperfections and are responsible for the useful property of ductility in metals, ceramics and crystalline
polymers.