Ordo Lectionum Missae

The Ordo Lectionum Missae (Known officially in English as Order of Readings for Mass  ), commonly referred to as OLM, is  the main liturgical lectionary used in the Roman Catholic Church. It contains the designated Scripture readings for the celebration of the Mass of Paul VI, encompassing selections (pericopes) from both the Old and New Testaments of the Bible.

History
The development of the Ordo Lectionum Missae was a response to the liturgical reforms initiated by the Second Vatican Council (1962-1965), with the aim of promoting active participation of the laity in the Mass. Prior to the council, the Roman Catholic Church adhered to a one-year cycle of readings, incorporating a limited selection of passages. The Ordo Lectionum Missae introduced a three-year cycle of readings (designated as Years A, B, and C) for Sundays, and a two-year cycle for weekdays (I and II), significantly expanding the number of Scripture passages read during Mass.

Between 1969 and 1980 the Latin text of the OLM came from the Vulgate until it was replaced by the Nova Vulgata in 1981 with its second edition.

Structure
The OLM is structured to align with the liturgical calendar and provides readings for every Sunday and major feast day in the Roman Catholic liturgical year.

Masses for Sundays and Major Feast Days are characterized by a structured selection of readings. This arrangement comprises the following components: In the context of Masses for Weekdays, Lesser Feasts, and Special Occasions, a similar structure is employed, resulting in a set of readings that might appear as only two but effectively encompass four distinct elements:
 * First Reading: Derived primarily from the Old Testament, with the exception of readings from the Acts of the Apostles during the Easter Season.
 * Responsorial Psalm: Predominantly drawn from the Book of Psalms, occasionally featuring other biblical "Canticles."
 * Second Reading: Mainly sourced from the Letters of Paul, supplemented at times by selections from other New Testament Epistles and the Book of Revelation.
 * Verse before the Gospel: Typically consists of a direct quotation from the Bible, although adaptations from biblical texts are sometimes incorporated.
 * Gospel: Each year is associated with one of the synoptic Gospels - Year A follows the Gospel of Matthew, Year B predominantly features Mark, and Year C is associated with Luke. The Gospel of John is primarily reserved for use during the seasons of Lent and Easter.
 * First Reading: This section incorporates semi-continuous readings, alternating between the Old Testament and New Testament, following a two-year cycle.
 * Responsorial Psalm: The majority of selections are sourced from the Book of Psalms, occasionally introducing other Canticles into the rotation. Similar to the First Reading, this follows a two-year cycle.
 * Verse before the Gospel: In its early edition, this component mainly featured "common" texts, but the current practice prescribes specific texts.
 * Gospel: This component remains consistent from year to year, featuring semi-continuous readings drawn from the Gospels of Mark, Matthew, and Luke, in that order.

Usage
The lectionary is the guide for selecting the assigned readings for each Mass, the passages align with the General Roman Calendar of 1969 which is followed by the majority of Catholics. It is used in the ordinary form of the mass of the Roman Catholic Church, in contrast with the traditional "extraordinary form" which is still used by a few groups that adhere to the traditional calendar.

It is also used by some Independent Catholic denominations.

Variations
Although the Ordo Lectionum Missae, containing the Nova Vulgata, is the standard lectionary in the Roman Catholic Church, the ordinary form of the mass is rarely said in Latin so various vernacular translations and adaptations of the OLM have been produced to accommodate different language communities as called for in Sacrosanctum Concilium. Each translation retains the three-year cycle for Sundays and the two-year cicle for weekdays and may make minor adjustments to align with local customs (Like some dioceses and countries retaining culturally relevant feast days from the old calendar).

Certain catholic congregations and religious orders have their own authorized modification of the lectionary.

The readings from the old misal came from the Latin Vulgate and were usually read in English before the homily to the faithful from an adapted version of the Douay-Rheims Version. After Vatican II, new bible translations were made to be used in the new liturgy. The following Bible Translations used in the Lectionaries of English-Speaking Countries:


 * JB: Jerusalem Bible – Australia, Ireland, New Zealand, Pakistan, South Africa
 * ESV-CE: English Standard Version, Catholic edition – India (formerly the RSV was used) England/Scotland/Wales (formerly the JB was used)
 * RSV-CE: Revised Standard Version, 2nd Catholic edition – Antilles and the Personal Ordinariates for former Anglicans
 * NRSV: New Revised Standard Version – Canada
 * NAB: New American Bible (2nd ed.) – United States, Philippines

Influence in other churches
The Ordo Lectionum Missae, developed within the Roman Catholic Church, has had a notable influence on liturgical practices in various Christian denominations and communities. While not universally adopted, its principles and structured approach to Scripture readings have been adapted first in the 1980s by the Consultation and then through the Revised Common Lectionary in 1992. The United Methodist Church and the Presbyterian Church U.S.A. replace readings from the deuterocanonical books while Anglican and Lutheran denominations retain them.