Which best describes acceleration? distance over time speed in a particular direction change in velocity over time

Acceleration is described as the rate of change of velocity for any given object, it could be an increase or decrease in the velocity, by its definition an object at constant velocity could be considered to be accelerating if the vector quantity of the velocity, that is its direction changes.

Acceleration is the rate of change in velocity over time. It is a vector quantity that shows the magnitude and direction of the object. An object is accelerating if a man in bike starts to move from rest and increases its pace over time.