Final answer:
The first coordinate of an ordered pair (x,y) is called the abscissa, representing the horizontal position along the x-axis in a Cartesian coordinate system.
Step-by-step explanation:
The first coordinate of the given ordered pair (x,y) is called the abscissa. This term specifically refers to the x-coordinate in a two-dimensional Cartesian coordinate system. When you are given an ordered pair (x,y), x denotes how far along the horizontal axis—the x-axis—the point is, and y denotes how far along the vertical axis—the y-axis—the point is. The x-axis measures distance horizontally to the right as positive, while moving to the left is considered negative. The y-axis measures distance vertically upwards as positive, with moving down regarded as negative.
In the presented system, graphs and maps often use this method to pinpoint locations on a flat surface. However, for three-dimensional space, an additional z-coordinate is used, which extends out of the 2D plane. Here, the coordinates are expressed as (x, y, z), where z represents the height above or below the plane defined by the x and y axes.