English: Apsidal precession. The orientation of an orbit is not fixed in space, but rotates over time. This orbital precession is also called apsidal precession. The image shows the rotation of the Moon's orbit within its orbital plane, i.e. the axes of the ellipse are changing their orientation. (Distances and sizes are not to scale.)

The Moon's major axis – the longest diameter of the orbit, joining its nearest and farthest points, the perigee and apogee, respectively – makes one complete revolution about every 8.85 Earth years, or 3,233 days, as it rotates slowly in the same direction as the Moon itself. The Moon's apsidal precession is distinct from, and should not be confused with its axial precession.