The word “Orthodox” comes from the Greek orthodoxos, meaning “of the right opinion”), true doctrine and its adherents. The Greek Fathers first used the word in early 4th-century Christianity. It forms part of the official title of the Greek-speaking church (Eastern Orthodox Church) and those in communion with it. Also including orthodox as part of their titles are some of the smaller Eastern churches, which separated from the rest of Christendom in the 5th century as a result of the Monophysite controversy concerning the question of two natures in Christ.
The Eucharistic liturgy of the Orthodox Church is a kind of mystery drama in which the advent of the Lord is mystically consummated and the entire history of salvation —the incarnation, death, and Resurrection of Christ the Logos, up to the outpouring of the Holy Sprit— is recapitulated. The Orthodox Church also believes that, within the eucharistic mystery an actual transformation of the eucharistic elements in bread and wine takes place whereas the Roman Catholic dogma of transubstantiation teaches that the substance of the bread and wine is changed into the body and blood of Christ, though the properties of the elements remain the same, when the priest consecrates the bread and wine. The essential and central happening in the Orthodox liturgy, however, is the descent of the resurrected Lord himself, who enters the community as “the King of the universe.” The Orthodox Church still preserves the liturgical gestures of the early church in addition to the liturgical gestures found in many Christian churches such as crossing oneself, genuflecting, beating oneself on the chest, and kneeling during prayer or when receiving the eucharistic elements. Other gestures of devotion and veneration practiced in the Orthodox Church, are kissing the altar, the gospel, the cross, and the holy icons. The theology of the Orthodox Church fixed the number of sacraments at seven. The New Testament mentions a series of “holy acts” that are not, strictly speaking, sacraments. The Roman Catholic Church recognizes a difference between such “holy acts,” which are called sacramentals, and sacraments, but the Orthodox Church does not make such strict distinctions. The “holy acts” of the Orthodox Church are symbolically connected to its most important mysteries. Hence, baptism consists of a triple immersion that is connected with a triple renunciation of Satan that the candidates say and act out symbolically prior to the immersions. Candidates first face west, which is the symbolic direction of the Antichrist, spit three times to symbolize their renunciation of Satan, and then face east, the symbolic direction of Christ, the sun of righteousness. Immediately following baptism, chrismation (anointing with consecrated oil) takes place, and the baptized believers receive the “seal of the gift of the Holy Spirit.
Here again the method to gain “knowledge” is the same as described before. This is due, of course, to the fact that the Roman Catholic Church, the Protestant Churches and the Orthodox Church have the same roots even if they differ on a many points of doctrine, rites, and rules.