* Deceleration: This term specifically refers to a decrease in speed.

* Negative acceleration: This term is more general and refers to any change in velocity that is in the opposite direction to the current velocity. This can include slowing down (deceleration) or changing direction.

It's important to note that deceleration and negative acceleration are not always interchangeable. Deceleration always implies a decrease in speed, while negative acceleration can also imply a change in direction without a decrease in speed.