How is acceleration defined in physics?

In physics, acceleration is defined as the rate of change of velocity over time. This means that it measures how quickly an object is speeding up, slowing down, or changing direction. When an object's velocity changes, it implies that either its speed or direction (or both) is varying, which can occur even when the object moves at a constant speed if it is changing direction.

Velocity itself is a vector quantity that includes both speed and direction, so understanding acceleration as its rate of change provides a comprehensive view of how motion is affected by forces acting upon the object. This is fundamental in the study of dynamics and kinematics, which explore the movement of objects and the forces influencing that movement. The other alternative definitions focus on time, distance, and displacement, but they do not encapsulate the complete essence of how acceleration relates to motion.