Fr.: période synodique
For planets, the mean interval of time between two successive → conjunctions with or → oppositions to the Sun. For example, → Mars has a synodic period of 779.9 days from Earth; thus Mars' oppositions occur once roughly 2.135 years. In comparison, the synodic period of → Venus is 583.9 days. If the sideral periods of the two bodies around the third are denoted T1 and T2, their synodic period is given by: 1/Tsyn = |1/T1 - 1/T2|.