The apparent size of the Moon varies because the orbit of the Moon is elliptical, and as a consequence at one time it is nearer to the Earth (perigee) than half an orbit later (apogee). The orbital period of the Moon from perigee to apogee and back to perigee is called the anomalistic month.
The appearance, or phase, of the Moon is due to its motion with respect to the Sun. It varies in a period of time called a lunation, also called synodic month; its duration is about 2 days longer than an anomalistic month. The age is the number of days since new moon.<span>[1]</span>
