The Y-coordinate is a numerical value that represents a point's vertical position on a two-dimensional graph or coordinate plane. In the Cartesian coordinate system, each point is defined by an ordered pair, typically written as x, y, where x is the horizontal position and y is the vertical position. The Y-coordinate indicates how far up or down a point is located from the origin, which is the point 0, 0. In this system, positive Y-coordinates indicate positions above the origin, while negative Y-coordinates indicate positions below it. For example, the point 3, 4 has a Y-coordinate of 4, meaning it is four units above the origin. Understanding the Y-coordinate is essential for graphing functions, analyzing data, and solving geometric problems.