Spacetime is equipped with an indefinite non-degenerate bilinear form, variously called the "Minkowski metric", the "Minkowski norm squared" or "Minkowski inner product" depending on the context. The Minkowski inner product is defined so as to yield the spacetime interval between two events when given their coordinate difference vector as argument. Equipped with this inner product, the mathematical model of spacetime is called Minkowski space. The analogue of the Galilean group for Minkowski space, preserving the spacetime interval (as opposed to the spatial Euclidean distance) is the Poincaré group.