Orthodoxy, which comes from the Greek word, "Ορθοδοξία," is derived as follows:
Ορθός, meaning 'right' or 'correct'
Δόξα / Δοξασία, meaning 'glory' / 'belief'
Therefore, when we refer to Orthodoxy, we refer to the study of the true belief.
By declaring ourselves as Orthodox, we declare that we are Christians who believe in Jesus Christ as God and in the Church He established. We are members of the, "One Holy, Catholic and Apostolic Church," (from the Nicene Creed) the Body of Christ.
The Orthodox Church, unlike the other churches or religious denominations, is the One, True, Church, which was founded by our Lord Jesus Christ and taught by the Apostles themselves. It began at the first Pentecost, when Jesus sent down the Holy Spirit upon his disciples (found in Acts, Chapter 2), and created the Orthodox Church.
Even the clergy of the Orthodox Church can be traced back to the Apostles themselves, and to Christ, in an unbroken line. All other Christian denominations broke away from the Orthodox Church at some point in time.
The Orthodox Church maintains the traditions and teachings of our Lord Jesus Christ from the beginning, without change. While we do live in an ever changing world, the Orthodox Church and the Orthodox Faith, is unchanging. For as it is written, "Jesus Christ is the same yesterday, today, and forever" (Hebrews 13:8). As such, we too must remain steadfast, holding true to the teachings of the Church.
Symbol of Faith
The Nicene Creed is our confession of Faith, drawn up by the First Ecumenical Council in Nicaea, 325 AD, and the Second Ecumenical Council in Constantinople, 381 AD. It is the expression of our fundamental beliefs as Orthodox Christians. Like the Orthodox Church, it too has remained unchanged.
I believe in one God, Father, Almighty, Maker of Heaven and Earth and of all things visible and invisible.
And in One Lord Jesus Christ, the Only-Begotten Son of God, begotten of the Father before all Ages. Light of Light, True God of True God, begotten not made, One in essence with the Father, through Whom all things were made. Who for us men and for our salvation came down from Heaven, and was incarnated by the Holy Spirit and of the Virgin Mary, and became Man. And was crucified for us under Pontius Pilate, suffered and was buried. And rose on the third day according to the Scriptures. And ascended into Heaven, and sitteth at the right hand of the Father. And He shall come again with glory to judge the living and the dead; Whose Kingdom shall have no end.
And in the Holy Spirit, the Lord, the Giver of Life, Who proceedeth from the Father, Who with the Father and the Son together is worshiped and glorified; Who spoke by the Prophets.
In One Holy, Catholic and Apostolic Church. I acknowledge One Baptism for the remission of sins. I look for the resurrection of the dead. And the life of the age to come. Amen.