Strong's G2229 · Greek

εἰ

e · ay

an adverb of confirmation; perhaps intensive of 2228; used only (in the New Testament) before 3303; assuredly

Scholarly Lexicons

Abbott-Smith Manual Greek Lexicon

 5 ἦ (μήν) , v.s. εἰ , iii, 7. 

G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain