This article is the first part of a series of publications covering the basic prayers of the Christian denominations. The series will cover the Hail Mary (Ave Maria), the Apostles’ Creed (Credo or Symbolum Apostolicum), and the Lord’s Prayer (Paternoster). The aim of the articles is to collect all Lithuanian variants of these prayers translated before 1700, to compare their lexical and syntactic structure, and to show their dependences and connections. The first part of the series introduces the concepts and methodology; furthermore, it analyses the shortest and most rarely attested prayer Hail Mary. The authors avoid the traditional term poteriai ‘prayers’ because of its multiple meanings: the Lithuanian term poteriai may refer to all three prayers at once, or just to the Lord’s prayer, or even more – the Rosary and smaller prayers. Rather, ‘basic prayers’ are understood as the prayers that each Christian should learn by heart according to his denomination, usually in their own language.