When someone say inshaallah ameen what is the reply?

When someone says "InshaAllah Ameen," it signifies their hope that something will happen if it's God's will. A common reply is to affirm their sentiment by saying "Ameen" in return, which expresses agreement and support for their prayer or hope. Alternatively, you can also say "InshaAllah" to reinforce the idea of trusting in God's plan.