In the Orthodox Church, this rite is usually called the Divine Liturgy, rather than the Mass. It is the most important sacrament (or mystery) of the Church, celebrated every Sunday and on feast days throughout the year (in some communities, particularly in monasteries, it is celebrated every day, except on the weekdays of Great Lent). The Divine Liturgy, which is always sung throughout, consists of two parts: the Liturgy of the Catechumens, and the Liturgy of the Faithful. The first conists of psalms, hymns, and an Epistle and Gospel reading. The second is focused on the rite of Holy Communion. Orthodox believe, as do Roman Catholics, that the bread and wine offered are changed truly and substantially into Christ's Body and Blood, although the Orthodox have not developed a technical explanation of this along the lines of the Roman Catholic doctrine of transubstantiation. Orthodox also believe that the Eucharist is a sacrifice, albeit an unbloody one; it is the selfsame Sacrifice offered by Christ on the Cross. The Holy Gifts are distributed in both kinds. The faithful receive a portion of the Body of Christ, together with a portion of the Precious Blood, from a spoon.
Everyone is welcome to attend services or mass in the church, but only a person who is an Orthodox Christian can receive Holy Communion in an Orthodox Church.
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Mass is the name of the Sunday service for Catholics and Orthodox Christians.
The Divine Liturgy or Eucharist is the main form of Orthodox worship. It is similar to the Mass of the Roman Catholics.
Orthodox Christians do not refer to it as mass, but the Divine Liturgy. What language it is performed in depends on the church's ethnicity, though most Orthodox churches in America do it mostly in English. If it is a Greek church, then it is partially in Greek; if Russian, then in Russian; etc. But, like I said, the majority is done in English. In Antiochian Orthodox Churches, the entire liturgy is in English.
Catholics and others are welcome to attend an Orthodox service, but they are not permitted to receive the Eucharist, as this is reserved for members of the Orthodox Faith alone.
They should go every Sunday, and at other times during the week when the Divine Liturgy (mass) is held. Not all Orthodox Christians go each week, but it is a requirement that they should not miss a Liturgy for more than 3 Sundays in a row.
Russian orthodox. Greek orthodox. Coptic orthodox. Antiochia orthodox. Eastern orthodox. Ethiopian orthodox.
Coptic Christians are divided into Orthodox Coptics, Catholic Coptics, and protestant Coptics, the first two would have a Catholic Mass, the protestant Coptics have lost the power to celebrate the Eucharist.
Under normal conditions a Roman Catholic cannot substitute a Coptic Mass, which is an Orthodox Church, for his Sunday obligation to assist at a Catholic Mass unless there is no Catholic Church in the area. However, a Catholic may attend a Coptic wedding or funeral in the same way he may attend a Protestant funeral or wedding.
They are called Eastern Orthodox Christians or just Orthodox Christians.
Mass is not typically celebrated in an Orthodox Church. In the Orthodox tradition, the central act of worship is the Divine Liturgy. The Divine Liturgy is a Eucharistic service that includes hymns, prayers, Scripture readings, and the consecration of bread and wine to become the body and blood of Christ. It is a reverent and mystical experience that is deeply rooted in ancient tradition.