Orthodox literally means "right way" and "right worship" from the Greek 'ortho" (right) "doxa" (way, doctrine).
Arianism is a heresy which denies the Divinity of Christ as well as the existence of the Holy Trinity. Arians believe that Christ was created. Orthodox Christians believe that Christ IS God and therefore not created. Arians are not Christians because if one denies the Divinity of God the Son - Christ - as well as the Holy Trinity, then one is not a Christian. See the Nicene Creed which defines the basis of Christian theology. Modern examples of Arianism include Mormonism and Jehovah's Witnesses.
A: There are many differences between Greek Orthodox Church and Russian Orthodox Church, so posing the question that broadly is meaningless. Regular Christianity is too heterogeneous if at all useful notion.
There are no priestesses in Greek Orthodoxy as it showed the difference between them and Pagan religions.
Russian Orthodox chruch is part of the Orhtodox Cannon, the oldest form of Christianity. The Church is part of the same group that includes the Greek, Armenian and other ORthodox Churchs. The only difference between the Russian and other Orthodox churches is their primary language, and other non-christian traditions like dances, prominant festivals, or supersticions. But as far as the rest of Christianity goes, the Orthodox's main difference is a unique date for Easter, their ties with the old testament, and their more strict christian lifestyle adhering to more fast days then any other sect of Christianity.
orthodox Christianity
The difference is between truth (Orthodox) and error (Baptists).
Christianity, Roman Catholic and Orthodox, and Islam
Orthodox Christianity.
It was Orthodox Christianity.
Western Europe is majority Catholic whiel Russia is majority Eastern Orthodox. Both are branches of Christianity, however.
Islam and Catholic/Orthodox Christianity.
The Greek Orthodox regard themselves as the Original Christianity.
A rift developed between Latin Christianity and Greek Christianity which then led to the schism between the Catholic and Orthodox Churches. The conflict between the two led to mutual distrust . The Orthodox Church was the church of the Byzantine Empire.