The Greek Ioudaios designates a person belonging to the Jewish people — ethnically, religiously, or both. In the New Testament it encompasses both ethnic identity and religious/cultural belonging to the covenant people of Israel.
The term Ioudaios carries enormous theological weight in the New Testament. John's Gospel uses it frequently in complex ways — sometimes distinguishing Judean authorities from Galilean Jews, sometimes describing those who rejected Jesus, sometimes those who believed. Paul's statement in Romans 1:16 — 'first to the Jew (Ioudaios), then to the Gentile' — establishes the salvation-historical priority of Israel while affirming the universal scope of the gospel. His declaration in Galatians 3:28 — 'neither Jew nor Gentile' — announces that in Christ the dividing wall is abolished. The term also appears in Jesus' words to the Samaritan woman: 'salvation is from the Jews (Ioudaios)' (John 4:22) — the covenant purposes of God were carried through this particular people to reach all people.