Why is the word "Amen" used often during prayer?
The Talmud (Shabbat 119b) indicates that AMEN is an acrostic formed from the first letter of the three Hebrew words El Melech Ne'eman (meaning the Lord is a Trustworthy King).
As a response by a congregation to prayer or as a declamation Amen means 'truly' or 'so be it'.
- Rabbi Alfred J. Kolatch
Great