The **Euclidean distance** between two points in [[Euclidean Space|euclidean space]] is the length of the line segment between them. It can be calculated from the [[Cartesian Coordinates|cartesian coordinates]] of the points using the [[Pythagorean Theorem|Pythagorean theorem]]: $ d(p, q) = \sqrt{(p_1 - q_1)^2 + (p_2 - q_2)^2 + ... + (p_n - q_n)^2} $