The "Horizontal Axis" refers to the line that runs left to right on a graph or chart. It is commonly used in various fields, such as mathematics and statistics, to represent the independent variable. For example, in a graph showing the relationship between time and distance, the horizontal axis might display time in seconds. In a Cartesian coordinate system, the horizontal axis is typically labeled as the X-axis. This axis helps to organize data visually, making it easier to interpret trends and relationships. Understanding the horizontal axis is essential for analyzing graphs in subjects like science, economics, and engineering.