An increase in speed during a given interval of time is called acceleration, not negative acceleration.

Here's why:

* Acceleration is the rate of change of velocity. Velocity includes both speed (magnitude) and direction.

* Positive acceleration means the velocity is increasing in the direction of motion. This could be an increase in speed or a decrease in speed if the object is moving in the negative direction.

* Negative acceleration means the velocity is decreasing in the direction of motion. This could be a decrease in speed or an increase in speed if the object is moving in the negative direction.

In simpler terms:

* If you're getting faster, you're accelerating.

* If you're getting slower, you're decelerating (which is a type of acceleration).

* The term "negative acceleration" is sometimes used, but it's more accurate to say "deceleration" or "acceleration in the opposite direction."