Ad orientem
Ad orientem, meaning 'to the east' in Ecclesiastical Latin, is a phrase used to describe the eastward orientation of Christian prayer and Christian worship, comprising the preposition ad (toward) and oriens (rising, sunrise, east), participle of orior (to rise). Ad orientem has been used to describe the eastward direction of prayer that the early Christians faced when praying, a practice that continues in the Eastern Orthodox Church, Oriental Orthodox churches, Mar Thoma Syrian Church, Assyrian Church of the East, as well as the Eastern Catholic and Eastern Lutheran churches.