STRONGS NT 3483: ναί

ναί, a particle of assertion or confirmation (akin to νή; cf. Donaldson, Cratylus § 189), from Homer down, yea, verily, truly, assuredly, even so: Matthew 11:26; Luke 10:21; Philemon 1:20; Revelation 1:7; Revelation 16:7; Revelation 22:20; ναί, λέγω ὑμῖν κτλ., Matthew 11:9; Luke 7:26; Luke 11:51; Luke 12:5; ναί, λέγει τό πνεῦμα, Revelation 14:13; it is responsive and confirmatory of the substance of some question or statement: Matthew 9:28; Matthew 13:51; Matthew 15:27; Matthew 17:25; Matthew 21:16; Mark 7:28; John 11:27; John 21:15; Acts 5:8 (); ; Romans 3:29; a repeated ναί, most assuredly (A. V. yea, yea), expresses emphatic assertion, Matthew 5:37; ἤτω ὑμῶν τό ναί ναί, let your ναί be ναί, i. e. let your allegation be true, James 5:12 (Buttmann, 163 (142); Winer's Grammar, 59 (58)); εἶναι or γίνεσθαι ναί καί οὐ, to be or show oneself double-tongued, i. e. faithless, wavering, false, 2 Corinthians 1:18f; ἵνα παῥ ἐμοί τό ναί ναί καί τό οὐ οὐ, that with me should be found both a solemn affirmation and a most emphatic denial, i. e. that I so form my resolves as, at the dictate of pleasure or profit, not to carry them out, ibid. 17 (cf. Winer's Grammar, 460 (429)); ναί ἐν αὐτῷ γέγονεν, in him what was promised has come to pass, 2 Corinthians 1:19; ἐπαγγελίαι ἐν αὐτῷ τό ναί namely, γεγόνασιν, have been fulfilled, have been confirmed by the event, 2 Corinthians 1:20 (cf. Meyer at the passage). It is a particle of appeal or entreaty, like the (English yea) (German ja): with an imperative, ναί ... συλλαμβάνου αὐταῖς, Philippians 4:3 (where Rec. has καί for ναί); ναί ἔρχου, Revelation 22:20 Rec.; so ναί ναί, Judith 9:12. (A classification of the uses of ναί in the N. T. is given by Ellicott on Philippians 4:3; cf. Green, 'Grit. Note' on Matthew 11:26.)