* Acceleration is the rate of change of speed. This means that whenever an object's speed changes, it's accelerating.

* The greater the change in speed, the greater the acceleration. If an object speeds up quickly, it has a higher acceleration than an object that speeds up slowly.

* The direction of the acceleration is determined by the direction of the change in speed. If an object speeds up, it has a positive acceleration in the direction of motion. If it slows down, it has a negative acceleration (often called deceleration) in the direction opposite to motion.

Example:

* A car going from 0 mph to 60 mph in 5 seconds has a higher acceleration than a car going from 0 mph to 60 mph in 10 seconds.

* A car slowing down from 60 mph to 0 mph also has acceleration, even though it's slowing down. This acceleration is negative because it's acting in the opposite direction of the car's motion.

Key Point: Acceleration doesn't just mean "going faster". It describes any change in speed or direction.