apogee & perigee

The Moon moves on an orbit which is not circular but elliptical, with the Earth at one focus. At one end of this ellipse it makes its closest approach to the Earth (356 410 km or 221 473 miles), known as perigee. At the other end it reaches its greatest separation (406 697 km or 252 722 miles), called apogee. The period between successive perigees or apogees is called the anomalistic month, equal to 27.56 days.

Inconstant Moon