A lectionary is a collection of scriptures from the Bible that is put together for the sake of study, worship or other uses. Lectionaries are a tradition in major Christian and Judaic worship dating as far back as 200 BCE, used as a way to schedule regular readings of a religion's given scripture in cycles. This schedule has changed over the years, and may include daily, weekly or yearly cycles that vary between branches.
The Catholic Mass Lectionary and the Revised Common Lectionary are two major examples of lectionaries used by the various branches of Christianity. Before lectionaries were used with wide popularity, the Catholic church created a three-year cycle to be followed, where every Sunday and certain feasts and events would have assigned amounts of verses read. This system carried over into most christian lectionaries to the modern day.
The Revised Common Lectionary is a relatively recent creation of the Consultation of Common Texts. It was officially released in 1994 for common usage and has an ABC cycle of three years like previous lectionaries. The cycle goes by the Gospel of Matthew, the Gospel of Mark and then the Gospel of Luke, with other Gospels used in liturgical periods such as Lent and Advent.