Here's a breakdown:

* Velocity: Velocity describes both the speed and direction of an object's motion.

* Change in velocity: This means how much the velocity of an object changes, either in speed or direction, or both.

* Unit of time: This could be seconds, minutes, hours, or any other unit of time.

Formula for Acceleration:

Acceleration (a) = (Change in velocity (Δv)) / (Time (Δt))

Example:

If a car accelerates from 0 m/s to 20 m/s in 5 seconds, its acceleration is:

a = (20 m/s - 0 m/s) / 5 s = 4 m/s²

This means the car's velocity increases by 4 meters per second every second.