Distance – Concept, measurement and differences with displacement

We explain what distance is in physics and mathematics, and how it is measured. Also, the relationship between distance and displacement.

The distance is equal to the length of a line that joins two points.

What is distance?

Distance, in physics and mathematics, is a scalar quantity that is measured in units of length, and that can be understood as the path between a point of origin A and a point of destination B. This path is normally equivalent to the length of a line that joins two points, being in a Euclidean plane.

The word distance comes from Latin distantia, made up of the prefix dis- (“Divergence” or “distance”) and the verb stare (“to be”). That is why it is often used in everyday language to point, literally or metaphorically, the space or time that separates two events or two objects.

The distance is measured, according to the International System (SI) of weights and measures, in units of length called kilometers (km), or in its derived units: meters (m), centimeters (cm), millimeters (mm), etc.

Distance and displacement

Do not confuse distance with displacement. The first is a scalar quantity, for the measurement of which the units of length are sufficient, while the displacement is a vector quantity. This difference means that your measurement, unlike distance, it also involves a direction, that is, a sense.

Both concepts can be differentiated if we think that the distance between a point A and a point B is the total length traveled when going from one to the other, while the displacement will only take into account the distance in a straight line between one and the other.

That is to say: suppose that between point A and point B there are 10 kilometers of separation, but that we decide to travel them by taking several laps, approaching point C and then another D, instead of going in a straight line, we will have traveled a total amount of kilometers much higher than the 10 that would have meant walking in a straight line. That is our distance traveled.

However, we will have traveled only 10 kilometers, because for the calculation of the displacement the route does not interest, but the starting and ending points.