Geom.; pl. -es; more commonly in the L. form abscissa, pl. abscissae; also Eng. abscissas. [L. abscissa (sc. linea a line) cut off; pa. pple. of abscindere: see ABSCIND.] Literally, a line or distance cut off; spec. the portion of a given line intercepted between a fixed point within it, and an ordinate drawn to it from a given point without it.
In Conic Sections: the segment (or segments) of a diameter (or in a hyperbola, a diameter produced), intercepted between the point where it is cut by an ordinate, and the bounding curve. In Rectilineal Coördinates, the segment of a given line, x, intercepted between the point where it is cut by another line, y, and that in which it is cut by a line parallel to the latter drawn from a given point without it, and called the ordinate.
1698. De Moivre, in Phil. Trans., XX. 192. The Abscisse corresponding to a certain Area in any Curve.
1748. Hartley, Observ. on Man, I. iii. § 2. 339. The Ordinates & Points of the Absciss being given, in the unknown Curve.
1798. in Phil. Trans., LXXXVIII. 7. It was found to be a very accurate parabola, the abscissa of which was 13.85 in.
1841. Young, Math. Dissert., I. 10. In what directions the positive abscissas and the positive ordinates are usually taken.
1871. B. Stewart, Heat, § 141. Let us … reckon the temperatures along a line of abscissae after the manner represented in the figure.
