'Minister' in the Bible

After some time Paul said to Barnabas, “Let us go back and visit the brothers and sisters (believers) in every city where we preached the message of the Lord, and see how they are doing.”

Get up and stand on your feet. I have appeared to you for this purpose, to appoint you [to serve] as a minister and as a witness [to testify, with authority,] not only to the things which you have seen, but also to the things in which I will appear to you,