The Greek deuteros means second — the ordinal number following first — and by extension 'again' or 'for the second time'. It is a frequently occurring word in the New Testament, bearing significant theological weight in certain key passages.
Deuteros is the word behind the concept of the 'Second Adam' and the 'new covenant'. Paul calls Christ 'the last Adam' (1 Corinthians 15:45) and 'the second man' (1 Corinthians 15:47 — deuteros anthropos), contrasting the first Adam who brought death with the Second Adam who brings life. This 'second' is not inferior to the first — it is the eschatological fulfillment that the first was always pointing toward. Hebrews uses deuteros repeatedly to contrast the old covenant with the new (Hebrews 8:7; 9:7; 10:9): 'He sets aside the first to establish the second.' The Second Coming (deuteran in Hebrews 9:28) will complete what the First Advent began. In biblical narrative, the 'second' often carries redemptive superiority: the younger over the older, grace over law, resurrection life over mortal life.