The velocity
of an object is the rate at which it changes its position with time.
It is a vector quantity and defined by an object's direction
of travel as well as its speed. The quantity which expresses how
fast something is moving, and in what direction.

Velocity has both
size and direction, so it is a vector quantity. The size of the
velocity is the same as the speed. A vector quantity which measures
both how fast something is moving and in what direction. It is the
rate of change of position.

For example, the velocity of a plane may be given as 560 mph on
a bearing of 068^{o}.