Life is complex. Part of this complexity stems from the fact that there are many relationships between seemingly unrelated events. Armed with mathematics, we seek to understand the world. Perhaps the most relevant ``real-world'' relation is {{CMD_7}} {{CMD_8}}the position of an object with respect to time.{{CMD_9}} {{CMD_10}} Our observations seem to indicate that every instant in time is associated to a unique positioning of the objects in the universe. You may have heard the saying, {{CMD_11}} {{CMD_12}}you cannot be two places at the same time,{{CMD_13}} {{CMD_14}} and it is this fact that motivates our definition for functions.