abscissa

noun2

1. •
   The first of the two terms by which a point is referred to, in a system of fixed rectilinear coordinate (Cartesian coordinate) axes.

   • The point (3,2) has 3 as its abscissa and 2 as its ordinate.
2. •
   The horizontal line representing an axis of a Cartesian coordinate system, on which the abscissa (sense above) is shown.