The rate of change of displacement of a body is called

The rate of change of displacement of a body is called Velocity.
Velocity The rate of change of position of a particle in a given direction is called its velocity. Thus velocity is displacement made by the body per unit time. Velocity is a vector quantity.

Speed The rate of change of position of particle irrespective of direction is called speed. It is measured by distance covered per unit time. Speed is a scalar quantity.