/ ˈæksɪs; NAmE / noun ( pl. axes / ˈæksiːz; NAmE /)
1.
an imaginary line through the centre of an object, around which the object turns :
Mars takes longer to revolve on its axis than the earth.
2.
( technical ) a fixed line against which the positions of points are measured, especially points on a graph :
the vertical / horizontal axis
3.
( geometry ) a line that divides a shape into two equal parts :
an axis of symmetry
The axis of a circle is its diameter
4.
[ usually sing. ] ( formal ) an agreement or alliance between two or more countries :
the Franco-German axis
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WORD ORIGIN
late Middle English : from Latin , axle, pivot .