The Greek adverb ethnikōs (ἐθνικῶς) means 'in the manner of Gentiles' or 'like a pagan.' It appears once in Galatians 2:14, in Paul's rebuke of Peter at Antioch: 'If you, though a Jew, live like a Gentile [ethnikōs] and not like a Jew, how can you compel Gentiles to live like Jews?'
Galatians 2:11–14 records one of the New Testament's most dramatic confrontations: Paul opposing Peter to his face. Peter had been eating freely with Gentile believers (living ethnikōs) until certain men from James arrived, after which he withdrew and separated himself, 'fearing those who belonged to the circumcision group.' Paul's accusation of hypocrisy cuts to the heart of Gospel logic: if the death of Christ has removed the wall between Jew and Gentile, acting as if it still stands is a betrayal of the Gospel (Ephesians 2:14). The word ethnikōs here is not used with contempt for Gentiles — Paul himself was the apostle to the Gentiles. It exposes Peter's inconsistency: he knew the Gospel truth but acted against it under social pressure.