In the beginning of the 19th century, the usual complex numbers and their introduction through computations with number-pairs or points in the plane, became a general tool of mathematicians. Naturally the question arose whether or not a similar "hypercomplex" number can be defined using points of n-dimensional space. As it turns out, such extension of the system of real numbers requires the concession of some of the usual axioms (Weierstrass 1863). The selection of rules of computation, which cannot be avoided in hypercomplex numbers, naturally allows some choice. Yet in any cases set out, the resulting number systems allow a unique theory with regard to their structural properties and their classification. Further, one desires that these theories stand in close connection with other areas of mathematics, wherewith the possibility of their applications is given.