What is the correct definition of acceleration?

Acceleration is defined as the change in speed and/or direction of an object. This definition encompasses not only an increase in speed but also a decrease (deceleration) and changes in direction, even if the speed remains constant. For instance, when a car makes a turn while maintaining a constant speed, it is experiencing acceleration because its direction is changing. This comprehensive view captures the full scope of what acceleration can entail in physics.

In contrast, the other definitions focus on more limited aspects. One option refers solely to the change in speed, which neglects the crucial aspect of directional change. Another suggests that acceleration is only about how quickly an object maintains its velocity, which does not accurately reflect the concept of acceleration because maintaining a constant velocity means there is no acceleration taking place. Lastly, the description of distance traveled over time pertains more to speed than acceleration. Thus, recognizing that acceleration includes both changes in speed and direction provides a clearer, more complete understanding of the term.