Christians (as well as Jews and Muslims) around the world say the world "Amen" countless times a day, both in personal prayer and the liturgy. For a large number of people it has become second nature, uttering the word without ever giving it a second thought. Unfortunately, for many people the word doesn't have a particular meaning and is said simply because it is at the end of a prayer.
However, the prayer has a deep spiritual meaning, one that is easily overlooked.
The word "Amen" is a Hebrew word that is used frequently in the Old and New Testaments. According to Bible Study Tools, "The verb form occurs more than one hundred times in the Old Testament ... [and] nearly seventy occasions in [all] the Gospels."
Jesus uses the word often in his preaching, frequently saying "Amen, amen I say to you ..." This word is usually translated as "truly" or "verily" in biblical translations and at its root signifies truth or the confirmation of a truth. In the Old Testament it typically signifies a full acceptance of what was previously spoken.
According to the Catholic Encyclopedia, "When Amen is thus used by Our Lord to introduce a statement He seems especially to make a demand upon the faith of His hearers in His word or in His power." In other words, Jesus seeks to elicit a full assent to his teachings by his followers while at the same time affirming his divine authority.
To further deepen its spiritual power, in some Latin translations of Nehemiah 8:6 the original "amen, amen" is rendered as fiat, fiat. This is an interesting translation as the Blessed Mother's "yes" at the Annunciation is known in Latin as her fiat. This Latin word is translated into English as "let it be done" and summarizes Mary's humble obedience to the Word of God. In this context the word "Amen" not only affirms what was spoken, but is pledge of allegiance to God in humble submission.
The early Christians adopted this word in a liturgical context, assigning it to the congregation where they would say "Amen" during the divine service, affirming what was spoken or prayed. Since then it has continued to be a central part of Christian prayer and is a single word with a great depth of spiritual meaning.