abscissas

Abscissas is the plural form of abscissa, a term in analytic geometry that refers to the x-coordinate of a point in a Cartesian coordinate system. In two dimensions, a point is written as (x, y), and the abscissa of the point is the value x. The abscissa represents the horizontal coordinate and can be positive, negative, or zero. The projection of the point onto the x-axis is the point (x, 0), whose distance from the origin is |x|.

In three dimensions, a point has coordinates (x, y, z). The abscissa remains the first component, while the other coordinates are typically called ordinates (y and z). In higher-dimensional spaces, the first coordinate is still referred to as the abscissa, with the remaining coordinates considered ordinates.

The term originates from the Latin abscissa, meaning “a cutting off” or “the cut-off part,” and has been used in analytic geometry since the era of Descartes to denote horizontal coordinates. In graphing, the abscissa often corresponds to the input variable in a function y = f(x); the values plotted along the horizontal axis are the abscissas.

Usage notes: both abscissas and abscissae are accepted plurals. In typical notation, the abscissa is denoted by x, while the corresponding y-coordinate is the ordinate. The concept connects to labeling, graphing, and coordinate descriptions across dimensions.