Oremus


Oremus is the invitation to pray, said before short prayers in the Catholic Mass and the Lutheran Divine Service, as well as other Western liturgies.
It is used as a single exclamation in the East, denoting the imperative "Pray" or "Stand for prayer" ; most commonly, however with a further determination, "Let us pray to the Lord", and so on. Louis Duchesne thought that the Gallican Collects were also introduced by the word "Oremus". That was not the case in the Mozarabic Rite, where the celebrant uses the word only twice, before the Agios and Pater noster.
Oremus is said in the Roman Rite before all separate collects in the Mass, Office, or on other occasions. It is also used before the Post-Communion, the offertory, and before the introduction to the Pater noster and other short prayers in the form of collects.
It appears that the Oremus did not originally apply to the prayer that now follows it. It is thought that it was once an invitation to private prayer, very likely with further direction as to the object, as is now the case in the liturgy for Good Friday. The deacon then said: Flectamus genua, and all knelt in silent prayer. After a time the people were told to stand up, and finally the celebrant collected all the petitions in one short sentence said aloud. Eventually this was simplified into the word alone preceding the prayer.