Distance

Distance and displacement describe different aspects of a journey. Distance is the total path length and is scalar. Displacement describes the change in position from start to finish, so it needs a straight-line magnitude and a direction.

Distance is the total length of the route travelled. It does not include a direction, so it is a scalar.

Describing motion begins with two measurements: a distance and a time interval. Distance is measured between two clearly identified positions. A time interval is measured between two clearly identified events, such as an object crossing a start line and then a finish line.

The distance travelled is measured along the actual path. Imagine walking around three sides of a rectangular field: your distance is the total length of all three sides. Displacement compares only your starting and finishing positions.