The abscissa represents the number corresponding to the point on the X axis on the coordinate map. For example, the abscissa of the point (2, 5) is 2. The horizontal coordinate of a point in a plane Cartesian coordinate system is measured by a line segment parallel to the X axis. The abscissa is usually opposite to the ordinate. It is also used in mathematical functions. The longitudinal axis of the coordinate is x, and the north from the origin is positive; The horizontal axis of the coordinate is y, which is positive from the origin to the east.