In 3-dimensional Euclidean space (e.g., simply "space" in Galilean relativity), the isometry group (the maps preserving the regular Euclidean distance) is the Euclidean group. It is generated by rotations, reflections and translations. When time is amended as a fourth dimension, the further transformations of translations in time and Galilean boosts are added, and the group of all these transformations is called the Galilean group. All Galilean transformations preserve the "3-dimensional" Euclidean distance. This distance is purely spatial. Time differences are "separately" preserved as well. This changes in the spacetime of special relativity, where space and time are interwoven.