syn·od·ic 
(sĭ-nŏdĭk) or syn·od·i·cal (-nŏdĭ-kəl)
(sĭ-nŏdĭk) or syn·od·i·cal (-nŏdĭ-kəl)adj.
1. Of or relating to a synod; synodal.
2. Relating to the period of time required for an object to complete a single orbital period, returning to the same position as observed from another object or position in space.
syn·odi·cal·ly adv.