In physical science, motion is defined as a change in position. It's not just about moving from one place to another, but also about a change in the object's location relative to a reference point.

Here's a breakdown:

* Motion: The act of changing position over time.

* Position: An object's location in space relative to a reference point.

* Reference Point: A fixed location used to determine the position of other objects.

For example:

* A car moving down the road is in motion.

* A tree standing still relative to the ground is not in motion.

It's important to note that motion is a relative concept. An object can be in motion relative to one reference point but stationary relative to another. For example, a passenger on a moving train is in motion relative to the ground but stationary relative to the train itself.