A book that contains scripture readings (pericopes) that are appointed to be read according to the cycles of the Liturgical Year in the services of the Church. The lectionary goes back at least to the 4th century, and some of the oldest Greek manuscripts of the New Testament that have survived are Byzantine Lectionaries.
The oldest form of the Lection is to have the text of Scripture with the beginning and ending of each pericope noted in the margin. This still essentially the format of the Slavic Gospel and Apostol. Contemporary Byzantine Lectionaries reflect a further development, in which each pericope is printed in the order in which it is read in the Church Year, and its beginning is included in the text, and the ending is a clear break.