ABSTRACT
The real axis is a straight line with a point O chosen as the origin, a positive direction, and a scale unit.
There is a one-to-one correspondence between the set of all real numbers R and the set of all points of the real axis, with each real x being represented by a point on the real axis separated from O by the distance |x| and lying to the right of O for x > 0, or to the left of O for x < 0.
