Illustration of a Cartesian coordinate plane. The first value in each ordered pair is the abscissa of the corresponding point.
In
mathematics, an
abscissa (plural
abscissae or
abscissæ or
abscissas) is the perpendicular distance of a point from the y  axis. Usually this is the horizontal coordinate of a point in a twodimensional rectangular
Cartesian coordinate system. The term can also refer to the horizontal axis (typically
xaxis) of a twodimensional graph (because that axis is used to define and measure the horizontal coordinates of points in the space). An
ordered pair consists of two terms—the abscissa (horizontal, usually
x) and the
ordinate (vertical, usually
y)—which define the location of a point in twodimensional rectangular space.

(\overbrace{x}^\text{abscissa}, \overbrace{y}^\text{ordinate})
In parametric equations
In a somewhat obsolete variant usage, the abscissa of a point may also refer to any number that describes the point's location along some path, e.g. the parameter of a parametric equation.^{[1]} Used in this way, the abscissa can be thought of as a coordinategeometry analog to the independent variable in a mathematical model or experiment (with any ordinates filling a role analogous to dependent variables).
Examples

For the point (2, 3), 2 is called the abscissa and 3, the ordinate.

For the point (1.5, 2.5), 1.5 is called the abscissa and 2.5, the ordinate.
See also
References

^ Hedegaard, Rasmus; Weisstein, Eric W. "Abscissa". MathWorldA Wolfram Web Resource. Retrieved 14 July 2013.
This article is based on material taken from the Free Online Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.
External links

The dictionary definition of abscissa at Wiktionary
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