* Speed changes: If an object speeds up or slows down, its velocity changes.

* Direction changes: Even if the speed remains constant, if the direction of motion changes, the velocity changes. This is because velocity is a vector quantity, meaning it has both magnitude (speed) and direction.

Here are some examples:

* A car accelerating from a stop sign: The car's speed increases, therefore its velocity changes.

* A ball thrown straight up in the air: The ball's speed decreases as it goes up, and then increases as it comes back down. Its velocity changes throughout the entire trajectory.

* A car turning a corner: The car's direction changes, even if its speed stays the same. Its velocity changes because its direction of motion changes.

In summary: Velocity changes whenever there's a change in speed, direction, or both.