Final answer:
The length of time it takes for the Moon to go through a complete cycle of phases is called the synodic period or the lunar month.
Step-by-step explanation:
The phases of the Moon
The length of time it takes for the Moon to go through a complete cycle of phases is called the synodic period or the lunar month. This period is about 29.5 days. It is longer than the Moon's orbital period because it takes into account the changing position of the Sun in the sky, which affects the illumination of the Moon. The different shapes of the Moon during its phases indicate different angles of illumination.