Question

what its velocity?please define it in a full sentence

Answer 1

The velocity of an object is the rate of change of its position with respect to a frame of reference, and is a function of time. Velocity is equivalent to a specification of an object's speed and direction of motion

Answer 2

The velocity of an object is the rate of change of its position with respect to a frame of reference, and is a function of time. Velocity is equivalent to a specification of an object's speed and direction of motion. 

In SI base units: m/s

Other units: mph, ft/s