/ˈsiːkwəns/
[noun] A set of things that follow one another in a particular order. It can refer to events, numbers, steps in a process, or scenes in a film.
Every time you say 'sequel', you are using the same Latin root as 'sequence' — both words are about following.
The story of 'sequence' begins in ancient Rome, with the Latin verb *sequi*, meaning 'to follow'. This was one of the most productive roots in the Latin language, giving rise to a wide family of words all built around the idea of one thing coming after another. From *sequi* came the noun *sequentia*, which meant 'a following' or 'a succession of things'. It was a logical, orderly word — the kind Romans used when they wanted to describe events or arguments that moved in a clear, connected line.
During the Middle Ages, Latin *sequentia* was adopted into the vocabulary of the Christian Church in a very specific way. Medieval monks and priests used it to describe a type of liturgical hymn that was sung after the Alleluia in the Mass — it literally 'followed' another part of the service. These chants were called *sequences*, and the word became deeply embedded in the musical and religious life of medieval Europe. It is a remarkable twist: a word we now associate with logic and order first entered common European use through sacred song.
From ecclesiastical Latin, the word passed into Old French as *sequence*, keeping much of its original meaning but gradually broadening beyond the church. Middle English adopted it from Old French in the late 14th century, and by the 1500s English writers were using 'sequence' to mean any ordered series of things — not just liturgical music, but cards in a game, steps in a plan, or links in a chain of reasoning.
The Latin root *sequi* was extraordinarily fertile in English. The chain of related words it produced is long and surprising. Latin *sequi* → Latin *sequela* → English 'sequel', meaning something that follows a story. Latin *sequi* → Latin *consequi* → Old French *conséquence* → English 'consequence', what follows from an action. Latin *sequi* → Latin *prosecuti* → Old French *poursuivre* → English 'pursue', to follow after someone. Even 'obsequious' comes from Latin *obsequium*, meaning 'compliance' — literally, following along submissively.
In modern English, 'sequence' has spread far beyond its original meaning of simple succession. Scientists speak of DNA sequences, mapping the precise order of chemical letters in genetic code. Filmmakers talk about action sequences, meaning a connected series of shots. Mathematicians define sequences as ordered lists of numbers following a rule. In every case, the original idea remains alive at the heart of the word: one thing following another, in an order that matters. The word has grown enormously, but it has never lost the shadow of that Latin verb *sequi* — to follow.