Affirmation. So it is. "Verily,* Verily" (Jhn 6:47).
Supplication. So let it be. "Truth,* Lord" (Mat 15:27).
Expectation. Let it be. "Surely,* I come" (Rev 22:20).
Confidence. It shall be. "Verily,* Verily" (Jhn 5:24).
Necessity. It must be. "Verily,* I say" (Jhn 3:3).
Certainty. It is. "Promises in Him, Amen"* (2Cr 1:20).
Acquiescence. Let it be. "Even* so, Father" (Mat 11:26).
* Same word in Greek.