Torque, moment of force or moment, is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. In Mathematical, torque is defined as the cross product of the lever-arm distance and force, which tends to produce rotation. Simple speaking, torque is a measure of the turning force on an object such as a flywheel or a bolt. Generally, its symbol is T, the Greek letter tau. As the torque is called moment, it is commonly represented M. The SI unit for torque is the newton metre (N•m). The units of pound-force-foot, pound-force inch, and ounce-force-foot are also used for toque. For all these units, the word "force" is often left out, such as pound-force-inch, abbreviate to simply "pound-inch".