Euclidean distance (L2 norm)

The Euclidean distance is the distance, “as the crow flies,” from one coordinate (or vector) to another coordinate (or vector). Recall that the L-p norm is given as

The Euclidean distance is the norm. Therefore, it is given as

As the Euclidean distance is often considered to be the most common and “natural” norm, the subscript is often omitted, and it is given just as .