Liturgy
Etymology
From Greek “leitourgia,” meaning a public service or work done for the people, from “leitos” (public, from “laos,” the people) plus “-ergon” (work) — literally “work of the people.” In ancient Athens a “liturgy” was a costly public duty a wealthy citizen funded, like outfitting a warship or a chorus. Christian usage transferred the word to the communal work of public worship.
noun · /LIT-er-jee/
The set, communal form of public worship followed by a religious tradition.
What it names
The fixed script of shared worship — the order of a service, as opposed to spontaneous or private prayer.
Example
Even lapsed for decades, he could recite the whole liturgy, its cadences worn into him like a childhood song.
Related idea
A ritual can be private or improvised; liturgy is specifically the fixed, communal, public form of worship — the shared script of the people.