The Greek deuteraios means 'on the second day' or 'coming on the second day'. It is a temporal adjective derived from deuteros (second). It appears only once in the New Testament.
Deuteraios appears in Acts 28:13, describing Paul's sea voyage: 'The next day (deuteraios) the south wind came up and on the second day we reached Puteoli.' This nautical log entry reflects the extraordinary care with which Luke recorded Paul's journey to Rome — the Acts account includes precise travel times, weather conditions, and geographic details that have repeatedly been verified by marine archaeology and classical scholarship. Luke's meticulous dating (including deuteraios) is evidence of eyewitness participation in the voyage. Theologically, the precision of Acts 27–28 reminds us that the gospel is grounded in real history — not mythological time but measured days, named ports, and counted hours.