The ratio of change in configuration to the original configuration is called strain.
Being the ratio of two like quantities, it has no dimensions and units.
Strain are of three types :
Linear strain in the direction of deforming force is called longitudinal strain and in a direction perpendicular to force is called lateral strain.
(3) Shearing strain : If the deforming force produces a change in the shape of the body without changing its volume, strain produced is called shearing strain.