A month measured by the orbit of the moon measured against the celestial sphere. The mean sidereal month is 27 days 7 hours 43 minutes 11.5 seconds.
The time it takes the Moon to complete one orbit of Earth and return to the same position among the stars. An average of 27.32166 days.
The 27.32166 day period of the Moon's orbit.
The average period of revolution of the Moon around the Earth in reference to a fixed star, equal to 27 days, 7 hours, 43 minutes in units of mean solar time.