 Space The two-dimensional plane is generalized to three-dimensional space by adding to the variables \(x\) and \(y\) a third variable \(z\) corresponding to the third dimension. The conventional orientation takes the first dimension to run from west to east, the second from south to north, and the third from below to above. Points are then triples, for example the point \((2, 5, -3)\) is 2 units to the east of the origin, 5 units to the north of it, and 3 units below it.