In special relativity we are only allowed to use inertial frames to assign coordinates to events. There are many different types of inertial frames. However, it is convenient to adhere to those with standard coordinates. That is, spatial coordinates which are right-handed rectilinear Cartesians based on a standard unit of length and time-scales based on a standard unit of time. We shall continue to assume that we are employing standard coordinates. However, from now on we shall make no assumptions, unless specifically stated, about the relative configuration of the two sets of spatial axes and the origins of time when dealing with two inertial frames. Thus, the most general transformation between two inertial frames consists of a Lorentz transformation in the standard configuration plus a translation (this includes a translation in time) and a rotation of the coordinate axes.