What is an Apostle?

Part 2 of Curiouscat's question: What exactly is an apostle (Paul says Jesus appeared to "The Twelve" but neither Thomas nor Judas was there, right?). Was Paul technically the 12th apostle and the replacement for Judas? Was Matthias really an apostle? Andronicus and Junias (Rom 16:7)are also called apostles, but I don't see those names anywhere else in lists of the apostles. There are other places, too, where apostles seem to mean more than twelve.

The term apostles was originally used to refer to the 12 disciples specially chosen by Jesus (Matthew 10:1-4; Mark 3:13-19; Luke 6:13-16) whom He then empowered to go out and preach the good news of the Kingdom of God with signs and miracles as well. Paul later goes so far as to describe the "things that mark an apostle-signs, wonders and miracles-were done among you with great perseverance.(2 Cor 12:12 NIV). Traditionally there were considered to be 12 apostles for the Jewish people and then Paul as the apostle to the gentiles (Romans 1:1-6). Later in the New testament, the term apostle seems to be used in a broader sense.

The word for apostle, apostolos, comes from the classical greek word apostello which means to send. It differs from the word pempo which means to send, in that in apostello the tie between the sender and the sendee is noted while pempo is just a verb for "to send". The term apostello connotes the idea that an envoy has the full powers of, and is the personal representative of the one sending him, in this case God. A close connection between the sender and the recipient is established. But the word used in the text is apostolos which is first a verbal adjective and then a noun. Apostolos was first used to refer to a cargo ship or a fleet of ships that had been sent out. Later it came to refer to a band of colonists sent overseas. It would seem that whenever the term is used there are two ideas that are always present: 1) an express commission, with the full authority of the sender; 2) being sent overseas.

In Acts 14:14, we find that Barnabas and Paul were considered apostles, and probably had been, since their commissioning via prayer, fasting and the laying on of hands (Acts 13:1-4) by the elders of the church that they had established in Antioch and as they were sent out by the Holy Spirit. At this point, in Acts 14, they are planting churches and then appointing elders in each of the churches. They appointed the elders in each church, with prayer and fasting, committing them to the Lord in whom they believed (14:21-23).

Apostles as seen in the New Testament church are those who, after working locally, are commissioned and sent overseas to minister. An apostle is a missionary church planter, a healer, a preacher, and a teacher. They appoint elders in the churches that they plant and work to develop faithful indigenous leadership. Their ministry is characterized by the powerful gifts of the Holy Spirit.