An apostle is one sent with delegated authority to represent and carry out the mission of the one who sent him.
The word apostle means "sent one." Scripture uses the term in more than one sense, though always with the idea of authorized representation and mission.
See in Scripture: Exodus 3:10–15; Luke 6:13; Acts 13:1–4; Hebrews 3:1; Ephesians 2:20