(1) A fundamental space of classical geometry, defined by a lack of boundaries and a lack of curvature. I.e. Euclidean space is both infinite and flat. A good abstraction for almost all real world based situations. Unless specifically mentioned otherwise, any reference to a space assumes the space to be Euclidean. Non-Euclidean spaces include hyperbolic and elliptic spaces, as well as the space-time of Special Relativity.

(2) A type of distance metric identical to a distance between points when measured with a ruler. Calculated as the square root of the sum of the squared x, y and z differences between coordinates. This is the default distance metric in almost all cases involving distances between points.