What does 'amen' mean? Why do we end prayers with 'amen'?

TL;DR:

Amen is an affirmation that something is true. When we say this at the end of a prayer, we are agreeing with the prayer and asking God to answer.

Amen is a Hebrew word meaning "truly" or "so be it," expressing agreement with a prayer and a request for God to grant it. In the Old Testament, amen is used to affirm God's justice and to praise Him (Deuteronomy 27:15-26; 1 Chronicles 16:36). In the New Testament, amen is often used in letters to praise God and affirm His glory (Ephesians 3:20-21; Romans 16:27). When Christians end their prayers with Amen, they express confident hope that God will hear and answer according to His will. It is a statement of trust in God's sovereignty and a reflection of submission to His perfect plan for our lives.

from the old testament

The Bible uses amen in both the Old and New Testaments. Almost half the occurrences appear in Deuteronomy as God announces punishments for specific sin (Deuteronomy 27:15–26). The people respond by saying "Amen" in agreement with God's justice and in acquiescence to His ways.
In the Old Testament, amen is linked with praise. For example, in 1 Chronicles 16:36, "… all the people said, 'Amen!' and praised the Lord." Nehemiah 5:13 and 8:6 similarly link saying amen with praising the Lord.

from the new testament

In the New Testament, letters often use amen in connection with praises to God, including letters from John (Revelation 1:6), Jude (Jude 1:25), Peter (1 Peter 4:11), and Paul (Romans 16:27). Here is one example: "Now to him who is able to do far more abundantly than all that we ask or think, according to the power at work within us, to him be glory in the church and in Christ Jesus throughout all generations, forever and ever. Amen" (Ephesians 3:20–21).

implications for today

When Christians pray and end their prayers with Amen they are asking that God would hear and grant their prayer. Amen is not a magical word nor a plea to conform God to our wills. Rather, it is a statement of confident hope that we make to a God who invites His children to come to Him in prayer (Hebrews 4:14–16; 10:19–23; Matthew 7:7–11). We trust that He knows what is best and desire that His will be done (Matthew 6:10; 26:39). When we pray according to God's will, we can be confident that He hears us and will answer according to His will (John 14:12; 1 John 5:14). When Christians pray and end their prayers with Amen, they are affirming their trust in God's sovereignty and His perfect plan. It is a declaration of faith, acknowledging that God hears, understands, and will answer according to His wisdom and timing. Amen reflects our submission to God's will, knowing that He is good and faithful and will answer for our good and His glory (Romans 8:28).

understand

Amen means "truly" or "so be it," expressing agreement and a request for God to grant the prayer.
Amen is used in both Testaments to praise God and affirm His justice and glory.
Ending prayers with Amen reflects trust in God's sovereignty and confidence in His perfect will.

reflect

When you say Amen at the end of your prayers, what does it mean for you in terms of trust and submission to God’s will?
How can you grow in your understanding of God's sovereignty when you pray, especially when praying for things that may not align with your desires?
How does the use of Amen in the Bible inspire you to affirm God's justice and glory in your own life?

engage

What does it mean to pray according to God's will, and how can we discern His will when we pray?
How does Amen reflect our faith in God's timing and wisdom in answering prayers?
How can we support each other in growing our trust in God's sovereignty, especially when facing difficult or unanswered prayers?