The Moon takes about 27.3 days to complete one full orbit around the Earth relative to the fixed stars; this is known as the sidereal month

. However, because the Earth is also orbiting the Sun, the Moon takes approximately 29.5 days to return to the same phase (e.g., from full moon to full moon), which is called the synodic month or lunar month

. In summary:

• Sidereal month (orbit relative to stars): ~27.3 days
• Synodic month (orbit relative to Sun/phase cycle): ~29.5 days

This difference arises because as the Moon orbits Earth, Earth itself moves along its orbit around the Sun, so the Moon must travel a bit further to reach the same Sun-Earth-Moon alignment