axis
noun [ C ]
uk/ˈæksɪs/ usplural axes uk/ˈæksiːz/ GRAPHS & CHARTS
one of two or more fixed lines on a graph:
horizontal/vertical axis We can label the axes - time is on the horizontal axis, and the amount (or value) of money is shown on the vertical axis.
an axis measures/shows/represents The vertical axis shows the rate of growth in inflation-adjusted GDP.