“Stationary” was defined in the first paragraph of this section: Let us take a system of coordinates in which the equations of newtonian mechanics hold good. In order to render our presentation more precise and to distinguish this system of coordinates verbally from others that will be introduced hereafter, we call it the “stationary system”.::::::::::: —Ibid. It is clear that the word “stationary” is used merely as a label, and implies no “absolute” aspects at all.