An act of worship; from a Greek word meaning an act of public service (e.g. donating a trireme for the Athenian navy). Paul uses the word (Phil 2: 30) for acts of service provided for him by converts. It came to be applied especially of service to God, and specifically of the Eucharist (e.g. by Justin Martyr, c. 150 CE). About 215 CE parts of the NT were being used in the liturgy of Hippolytus at Rome, and Luke–Acts was fundamental in establishing the basis of a Christian calendar.