The distance to the Sun is defined as one astronomical unit, or A.U.

If two points are on the same ray in the plane, their distance is defined as the Euclidean distance.

Otherwise, their distance is defined to be the sum of the Euclidian distances of these two points to the origin.

This distance is defined as the thermal entrance length, which is important for engineers to design efficient heat transfer processes.

On the positive real numbers, the (hyperbolic) distance function can be defined.

This distance is defined as the d-value of the sensory receptor.

The distance between X and Y can be defined to be the cost.

Kendall tau distance can also be defined as the total number of discordant pairs.

When u and v are unreachable from each other, their distance is defined to be infinity .

The intrinsic flat distance between two integral current spaces is defined as follows: