What do we call the rate of change of displacement?

The rate of change of displacement is referred to as velocity. Displacement is a vector quantity that measures the change in position of an object, and velocity describes how quickly this change occurs in a specific direction. It provides insight not just into how fast an object is moving but also the direction of that movement, making it a vector quantity as well.

While speed measures how fast an object moves regardless of direction, velocity specifically incorporates the direction aspect, thus differentiating it from mere speed.

Acceleration, on the other hand, is the rate of change of velocity, indicating how an object's velocity changes over time, while momentum is a measure of the quantity of motion an object has, defined as the product of its mass and velocity.