The word 'synod' entered English in the fourteenth century from Late Latin 'synodus,' borrowed from Greek 'sýnodos' (σύνοδος), meaning 'a meeting,' 'an assembly,' or 'a conjunction.' The Greek compound joins 'syn-' (σύν, together, with) and 'hodós' (ὁδός, road, way, journey). The literal meaning is 'a traveling together' or 'a meeting on the road' — people who have converged from different directions onto the same path.
The Greek prefix 'syn-' (together) comes from PIE *sem- (one, together), which also produced Latin 'simul' (at the same time — source of 'simultaneous,' 'similar,' 'simulate,' 'ensemble'), Latin 'semel' (once), Old English 'same,' and Sanskrit 'sama' (even, equal). The prefix appears in hundreds of English words: 'synonym' (named together — same meaning), 'synchronize' (time together), 'synthesis' (putting together), 'sympathy' (feeling together), 'symphony' (sounding together), 'system' (standing together), 'syllable' (taken together), and 'symbol' (thrown together).
The element 'hodós' (road, way) is less immediately familiar but equally productive. 'Method' (from Greek 'méthodos,' meta + hodós — 'a way of pursuit,' a systematic approach). 'Episode' (from 'epeisódion,' 'a coming in upon the road' — an incident that enters the main narrative). 'Exodus' (from 'éxodos,' 'a way out' — a departure, most famously the Israelites' departure from Egypt). 'Period' (from 'períodos,' 'a going around' — a circuit, hence a complete cycle
In Christian usage, a synod is a formal gathering of church officials — bishops, clergy, and sometimes laity — to discuss and legislate on matters of doctrine, discipline, and governance. The term was used from the earliest centuries of Christianity. The Council of Nicaea (325 CE), which formulated the Nicene Creed, is the most famous of the early synods (also called 'ecumenical councils'). Different Christian traditions use 'synod' differently: in Roman Catholicism, a synod may be convened by the Pope; in Eastern Orthodoxy, the Holy
The astronomical sense of 'synod' is also significant. A 'synodic period' is the time it takes for a celestial body to return to the same position relative to the sun as seen from Earth — literally a 'coming together again' of the same alignment. This astronomical usage preserves the original Greek sense of 'sýnodos' as a conjunction or meeting point.
The word 'synod' thus unites the sacred and the astronomical, the institutional and the cosmic. A church synod is a gathering of minds traveling toward consensus. A synodic period is a gathering of celestial bodies into alignment. In both cases, the etymological image holds: separate paths converging into a shared road.