An axis is a line with respect to which a curve or figure is drawn, measured, rotated, etc. The most common axes encountered are commonly the
mutually perpendicular Cartesian axes in the plane or in space.
The plural of "axis" is "axes," pronounced "ax-ees."
The term is also used to refer to a line through a sheaf
of planes (Woods 1961; Altshiller-Court 1979, p. 12).
