The Greek word diakonos comes into the English language as "deacon."
The term basically means to serve. It is used of ordinary servants in a secular sense (Jn. 2:5, 9) or of those who serve generally in the cause of Christ (rendered "minister" in 1 Cor. 3:5; 2 Cor. 3:6; Eph. 3:7). It can even be employed of those who serve Satan (2 Cor. 11:15).
The word takes on a technical sense, deacons, in some passages (Phil. 1:1). The qualifications for this special work in the church are found in 1 Timothy 3:8-13.
Diakonos is used of Phoebe in Romans 16:1, though one should not assume that she was a "deaconess" in any official sense. The servants mentioned in Acts 6:1ff may, or may not, have been deacons in a formal way. The evidence is inconclusive.