The word apostle or apostolos is from the Greek, meaning an ambassador; one who is sent; a delegated authority. The word was used for high ranking naval officers in classical Greek times. An apostle of Jesus Christ was the highest ranking official in the local churches, 1 Cor. 12:28.
Apostles of Jesus Christ were appointed by God the Father for the purpose of establishing churches and spreading new truth, Eph. 3:1‑10. There were both the spiritual gift and office of apostleship. The spiritual gift was the divine enabling to function as an apostle, Eph. 4:11, 1 Cor. 12:28, 29. The office of apostleship was the authority to function as an apostle, Rom. 1:5, Acts 1:25, Gal. 2:8.
Some of the uses of apostolos outside of the Bible are:
In the classical Greek period (4th and 5th centuries B.C.), apostolos was used by Lysias and Demosthenes to refer to the commander of a naval expedition. When the Athenians went to war, there was a number of men qualified to command the fleet. One of these was elected by lot and sent to the fleet to command it. He was called apostolos.
During the Hellenistic period (323 B.C. and following) apostolos was used to refer to a person commissioned and authorized by one of the gods.
In the Papyri of the koine period apostolos was used to refer to a civil agent sent to transact official business.
In the New Testament, the apostles of Jesus Christ fall into two classes:
The apostles of Jesus Christ to Israel, Luke 6:12‑16. These were appointed by Jesus Christ according to the will of God the Father. These men were authorized to announce to Israel that their Messiah was present; and they were endowed with miraculous powers, Luke 9:1, 2.
The apostles of Jesus Christ to the church. These included the eleven disciples (Acts 1:26), Paul (Rom. 1:1, etc.), James the brother of Christ (Gal. 1:19) and Barnabas (Acts 14:14).
An apostle had to have the spiritual gift of apostleship. The gift was provided by Jesus Christ after His ascension into heaven, Eph. 4:8‑11. The gift was imparted by the Holy Spirit on the day of Pentecost, 1 Cor. 12:11; Acts 2.
The apostle received his gift and office by the sovereign decision of God the Father, 1 Cor. 1:1; 12:18; Eph. 1:1; Col. 1:1.
The apostle had to have been an eyewitness of the resurrected Lord, Acts 1:22; 1 Cor. 9:1.
An apostle was endowed with miraculous powers of miracles, Heb. 2:4; 2 Cor. 12:12.
An apostle had success in evangelism, 2 Cor. 3:1‑3; Gal. 2:7‑9.
An apostle had the capacity to suffer patiently, 2 Cor. 12:12.
Apostles received and communicated new revelation, Eph. 3:2-6.
Apostles communicated the gospel effectively and people accepted Christ in response to their preaching, 1 Cor. 9:1; Gal. 2:7‑9.
Apostles helped organize local churches and appointed officers, Acts 14:23; Tit. 1:5.
Apostles trained new believers in doctrine, 1 Thess. 1:5 to 2:12.
Apostles had the authority to administer discipline to believers, Acts 5:1‑10; 1 Tim. 1:20; 1 Cor. 4:21; 2 Cor. 13:2.
The apostle had authority over all local churches because he was the channel of New Testament revelation. Since the time of the apostles, no one has been given authority over more than one local church.
The apostle Paul was the most grace oriented apostle. He realized that he was the least deserving to be an apostle, 1 Cor. 15:9. He was the most productive because of grace, 1 Cor. 15:10. There were false apostles who communicated false information, 2 Cor. 11:13; Rev. 2:2.