The word 'synagogue' is Greek in form but Jewish in function, and the tension between these two facts tells a story about how languages interact when cultures meet.
The Greek word 'συναγωγή' (sunagōgḗ) is a straightforward compound: 'σύν' (sun, together) plus 'ἀγωγή' (agōgḗ, a leading, from ἄγειν, agein, to lead). In classical Greek, it simply meant 'a bringing together' or 'a gathering.' It had no specifically religious connotation.
The word acquired its Jewish religious meaning in the third century BCE, when Jewish scholars in Alexandria translated the Hebrew Bible into Greek — the version known as the Septuagint. They needed Greek equivalents for Hebrew religious terms. The Hebrew 'בֵּית כְּנֶסֶת' (beit knesset) — literally 'house of assembly,' from the root k-n-s meaning to gather or assemble — was rendered as 'synagōgḗ.' The translation was accurate: both words fundamentally mean a place where people come together
The synagogue as an institution arose during or after the Babylonian exile (6th century BCE), when Jews, deprived of the Temple in Jerusalem, developed local houses of prayer, study, and assembly. Unlike the Temple, which was a place of sacrifice overseen by priests, the synagogue was communal and democratic — a place for reading Torah, for prayer, and for communal decision-making. The word's meaning as 'assembly' rather than 'temple' reflects this fundamental character.
The Greek root 'agein' (to lead, to drive, to bring) is among the most productive in the English vocabulary. A 'pedagogue' is one who leads (agōgos) children (paidos). A 'demagogue' leads the people (dēmos). A 'mystagogue' leads initiates into mysteries. An 'agora' is a place of gathering (from the same root, via a different formation). The word 'act' may also be distantly related through the Proto-Indo-European root *ag- (to drive, to lead).
The Greek prefix 'sun-' (together) is equally productive: 'synonym' (same name together), 'synthesis' (a putting together), 'sympathy' (feeling together, with sun- becoming sym- before labial consonants), 'synod' (a coming together, a meeting), 'synchronize' (to time together).
The word entered Latin as 'synagōga' in the early centuries of Christianity, and Latin transmitted it to the medieval European languages. Old French 'sinagoge' became Middle English 'sinagoge' by the twelfth century, eventually respelled to reflect the Greek original more closely as 'synagogue.'
The relationship between 'synagogue' and 'Knesset' deserves special note. The modern Israeli parliament is called 'הכנסת' (HaKnesset, The Assembly), from the same Hebrew root k-n-s that originally produced 'beit knesset.' So the Greek translation of the Hebrew word for 'assembly' gives us 'synagogue,' while the Hebrew original gives modern Israel the name of its legislature. The two words — one Greek, one Hebrew — are semantic twins separated by language and two and a half millennia.