For a church to be Orthodox it will need to have a Bishop.

The Greek Old and New Testament writings refer to the bishop as ἐπίσκοπος (episkopos)
Definition: Overseer or bishop, a leader in a local church, an extension of one who guards, supervises, and helps.

This word in Greek and Latin was altered slightly when entering into the Germanic lanuage family.

English – bishop
German – bischof
Frisian – biskop
Dutch – bisschop
Danish – biskop
Faroese – bishop
Icelandic – biskup
Norwegian – biskop
Swedish – biskop

Episkopos/Bishop usages in Old Testament Greek Septuagint LXX

The appointed duty of(Episkopos) Eleazar the son of Aaron the priest is the oil for the light, the sweet incense, the daily grain offering, the anointing oil, the oversight of all the tabernacle, of all that is in it, with the sanctuary and its furnishings. (Numbers 4:16)

But Moses was angry with the officers of the army, with the captains over thousands and captains over hundreds, who had come from the battle (Numbers 31:14)

Then Gaal the son of Ebed said, “Who is Abimelech, and who is Shechem, that we should serve him? Is he not the son of Jerubbaal, and is not Zebul his officer? Serve the men of Hamor the father of Shechem; but why should we serve him? (Judges 9:28)

And Jehoiada the priest commanded the captains of the hundreds, the officers of the army, and said to them, “Take her outside under guard, and slay with the sword whoever follows her.” For the priest had said, “Do not let her be killed in the house of the Lord.” (2 Kings 11:15)

And all the people of the land went to the temple of Baal, and tore it down. They thoroughly broke in pieces its altars and [a]images, and killed Mattan the priest of Baal before the altars. And the priest appointed officers over the house of the Lord. (2 Kings 11:18)

Then they gave the money, which had been apportioned, into the hands of those who did the work, who had the oversight of the house of the Lord; and they paid it out to the carpenters and builders who worked on the house of the Lord, (2 Kings 12:11)

And the men did the work faithfully. Their overseers were Jahath and Obadiah the Levites, of the sons of Merari, and Zechariah and Meshullam, of the sons of the Kohathites, to superviseOthers of the Levites, all of whom were skillful with instruments of music, (2 Chronicles 34:12)

Joel the son of Zichri was their overseer, and Judah the son of Senuah was second over the city. (Nehemiah 11:9)

and their brethren, mighty men of valor, were one hundred and twenty-eight. Their overseer was Zabdiel the son of one of the great men. (Nehemiah 11:14)

Also the overseer of the Levites at Jerusalem was Uzzi the son of Bani, the son of Hashabiah, the son of Mattaniah, the son of Micha, of the sons of Asaph, the singers in charge of the service of the house of God. (Nehemiah 11:22)

This is the portion from God for a wicked man, The heritage appointed to him by God. (Job 20:29)

“Instead of bronze I will bring gold, Instead of iron I will bring silver, Instead of wood, bronze, And instead of stones, iron. I will also make your officers peace, And your magistrates righteousness. (Isaiah 60:17)

Episkopos/Bishop usages in New Testament

Therefore take heed to yourselves and to all the flock, among which the Holy Spirit has made you overseers, to shepherd the church of God which He purchased with His own blood. (Act 20:28)

Paul and Timothy, bondservants of Jesus Christ, To all the saints in Christ Jesus who are in Philippi, with the bishops and deacons: Grace to you and peace from God our Father and the Lord Jesus Christ. (Philippians 1:1-2)

A bishop then must be blameless, the husband of one wife, temperate, sober-minded, of good behavior, hospitable, able to teach; (1 Timothy 3:2)

The second [epistle] unto Timothy ordained the first bishop of the Ephesians, from Rome, when Paul was brought before Nero the second time. (2 Timothy 4:22 Textus Receptus)

For a bishop must be blameless, as a steward of God, not self-willed, not quick-tempered, not given to wine, not violent, not greedy for money, (Titus 1:7)

It was written to Titus, ordained the first bishop of the church of the Cretians, from Nicopolis of Macedonia. (Titus 3:15 Textus Receptus)

For you were like sheep going astray, but have now returned to the Shepherd and Overseer of your souls. (1 Peter 2:25)

There is a clear chain of authority extending all the way back to the Apostles who appointed Bishops.  The trandition has been to ordain Bishops through the laying on of hands from Apostles to bishops to bishops to bishops until our present time. In this way the traditions both oral and scripitural are handed down throughout the ages. This unbroken chain of bishops is referred to as Apostolic Succession. It is important for the bishops to not alter the traditions through innovation. While some bishops might have the unbroken chain of ordinations, changes in the church which introduction innovations and heresy will invalidate the Apostolic Succession

One of the most tragic reforms of Gregory the 7th was the super-elevation of the Papal Episcopacy. The document Dictatus Papae A.D. 1075 made revolutionary claims about the Roman Church and the Roman Pontiff. While there were times in the previous centuries when the Bishop of Rome tried to enforce his edicts on the Church Catholic, he was always kept in check by The Holy Councils, the emperor and the faithful.

Churches Claiming Apostolic Succession: Chain of Bishops back to the Apostles

Roman Catholic Church

Ecumenical Patriarchate of Constantinople
Patriarchate of Alexandria
Patriarchate of Antioch
Patriarchate of Jerusalem
Patriarchate of Moscow
Patriarchate of Serbia
Patriarchate of Romania
Patriarchate of Bulgaria
Patriarchate of Georgia
Church of Cyprus
Church of Greece
Church of Poland
Church of Albania
Church of the Czech Lands and Slovakia

Church of the Genuine Orthodox Christians of Greece-K
Church of the Genuine Orthodox Christians of Greece-K
Autonomous Orthodox Metropolia of North and South America and the British Isles
Holy Orthodox Church in North America (HOCNA)
Russian True Orthodox Church (RTOC)

Assyrian Church of the East (Disagreement Council of Ephesus 431)
Coptic Christians (Disagreement Council of Chalcedon 481)

Lutheran Church of Sweden

The Church of England

*It is not the purpose of this article to determine which line of bishops is truly Orthodox. Even within these lists are strange irregularities. These can be attributed to competing bishops, contradictory information, missing dates and national conquests.