Apart from Acts 14:4, on every other occasion Luke uses the term apostle
to refer to the twelve disciples that Jesus called to follow him, learn from him and bear witness to him. They are thus the men whom Jesus chose at the outset of his ministry (Luke 6:12–16).1 The term itself implies the sending of a person to convey news, a role similar to that of an envoy,2 where the one sent bears the authority of the person who sent him.3
2 until the day when he was taken up, after he had given commands through the Holy Spirit to the apostles whom he had chosen.