How is acceleration defined?

Acceleration is defined as the change in velocity over time. This concept plays a critical role in physics, particularly in understanding how the speed and direction of an object change during its motion. Velocity, which incorporates both speed and direction, can vary in magnitude (speed) or in direction itself (such as turning or changing course). Thus, when discussing acceleration, it encompasses any alteration in velocity, whether an increase or decrease in the speed of the object or a change in the direction of its movement.

This distinction highlights why the other definitions do not accurately capture the complete essence of acceleration. While change in speed is a component of acceleration, it fails to include changes in direction. The rate of change of displacement refers to velocity, not acceleration, which further confirms that the correct understanding of acceleration is rooted in the broad definition relating to velocity. Similarly, speed in a given direction pertains to velocity rather than directly defining acceleration. Therefore, the comprehensive and precise definition of acceleration refers specifically to the change in velocity.