The Greek particle nai (ναί) is the standard word for 'yes' or 'indeed.' It is a strong affirmative, often used to confirm what has just been stated. It appears about 33 times in the New Testament. Unlike vague agreement, nai is a direct, unambiguous affirmation — it is the opposite of ou (no).
The theological weight of nai is most concentrated in 2 Corinthians 1:18–20: 'For the Son of God, Jesus Christ, who was preached among you by us — by me and Silas and Timothy — was not Yes and No, but in him it has always been Yes (Nai). For no matter how many promises God has made, they are Yes (Nai) in Christ. And so through him the Amen is spoken by us to the glory of God.' Christ is the cosmic Yes of God — every divine promise finds its affirmation and fulfillment in Him. This makes the gospel not a tentative offer but an unequivocal commitment. Revelation 22:20 ends with this same divine affirmation: He who testifies says, Yes (Nai), I am coming soon (Revelation 22:20).