A function is a relation (such that for each input, there is exactly one output) between sets. The formula and the graph are merely descriptions of this relation. {{CMD_81}} {{CMD_82}} A formula {{CMD_83}}describes{{CMD_84}} the relation using symbols. {{CMD_85}} A graph {{CMD_86}}describes{{CMD_87}} the relation using pictures. {{CMD_88}} The {{CMD_89}}function is the relation itself{{CMD_90}}, and is independent of how it is described. {{CMD_91}}