The y-axis is one of the two main lines on a graph, typically running vertically. It helps us measure and display values, such as height, temperature, or any other quantity. When you look at a graph, the y-axis usually shows the dependent variable, which changes in response to the independent variable plotted on the x-axis. In a simple graph, like a bar chart or line graph, the y-axis allows us to compare different data points easily. For example, if you were graphing the growth of a plant over time, the y-axis would represent the height of the plant, while the x-axis would show the days or weeks of growth.