 The length of the line segment between these points defines the unit of distance and the direction from the origin to the second point is defined as the "positive direction".This line segment may be translated along the line to build longer segments whose lengths correspond to multiples of the unit distance.In this manner real numbers can be associated to points on the line (as the distance from the origin to the point) and these are the Cartesian coordinates of the points on what may now be called the real line.