* Velocity is a combination of speed and direction.

* Acceleration is the rate of change of velocity.

So, if something is traveling at a constant velocity, it's not accelerating.

Here's an example:

* A car driving at 60 mph due east has a constant velocity.

* If the car maintains that speed and direction, it's not accelerating.

What *can* accelerate while traveling at a constant speed?

* Direction: If the car in our example turns a corner, it's changing its direction, therefore changing its velocity, and thus accelerating even if it's maintaining a constant speed.