What term describes the rate at which velocity changes over time?

The term that describes the rate at which velocity changes over time is acceleration. Acceleration quantifies how quickly an object's velocity increases or decreases. It can refer to an increase in speed (positive acceleration), a decrease in speed (often referred to as deceleration), or a change in direction while maintaining speed.

In contrast, deceleration specifically refers to a reduction in speed, which is a type of acceleration but does not capture the full range of changes in velocity. Speed is a measure of how fast an object is moving but does not incorporate direction or changes over time, making it distinct from acceleration. Velocity, while also a measure of speed, includes direction and only indicates the current state of motion rather than how that state is changing over time. Thus, acceleration is the most accurate term to describe the change in velocity.