* Acceleration is the rate of change of velocity. Velocity includes both speed (how fast an object is moving) and direction.
* Constant speed means the object is moving at the same rate, but its direction could be changing.
Examples:
* A car driving in a circle at a constant speed: The car has a constant speed, but it's accelerating because its direction is constantly changing.
* A ball thrown straight up: The ball's speed decreases as it goes up, and increases as it comes down. This means it's accelerating even though its speed isn't constant.
In short: Acceleration requires a change in velocity, and a change in velocity can occur either through a change in speed or a change in direction (or both).
