Gaius my host (Γαιος ο ξενος μου). Perhaps the same Gaius Rev 1. Corinthians 1:14 (Acts 19:29; Acts 20:4), but whether the one Rev 3. John 1:1 we do not know. Ξενος was a guest friend, and then either a stranger (Matthew 25:35) or a host of strangers as here. This Gaius was plainly a man of some means as he was the host of all the church. Erastus (2. Timothy 4:20) was "the treasurer of the city" (ο οικονομος της πολεως), one of the outstanding men of Corinth, the "steward" (house-manager) or city manager. See Luke 12:42; Luke 16:1. He is probably the administrator of the city's property.

Quartus (Κουαρτος). Latin name for fourth.