synodic period
time between two passes of an object in front of a distant star seen from another orbiting object
en-US/sɪˈnɑdɪk ˈpiɹiəd/
en-GB/sɪnɒdɪk ˈpɪəɹɪəd/
time between two passes of an object in front of a distant star seen from another orbiting object