On a Cartesian coordinate system, the abscissa is the vertical line

Explanation

The abscissa is the x-coordinate of a point, its horizontal distance from the vertical axis, while the ordinate is the y-coordinate, the vertical one. A classic classroom mnemonic: go "along the corridor, then up the stairs": first measure along the horizontal axis, then climb. The word abscissa comes from Latin abscindere, "to cut off", because the segment was cut off from the axis.