1. Change in Speed: This is the most straightforward way. If the object is moving faster or slower, its velocity is changing.

* Example: A car accelerating from a stop sign is increasing its speed, therefore its velocity is changing. A car slowing down to a stop is decreasing its speed, also changing its velocity.

2. Change in Direction: Even if the object's speed remains constant, its velocity can change if its direction changes. Remember, velocity is a vector quantity, meaning it has both magnitude (speed) and direction.

* Example: A car traveling at a constant speed around a curve is changing direction, therefore its velocity is changing even though its speed remains the same.

In summary: Velocity changes when an object's speed changes, direction changes, or both change.