The word written on the Doors of Durin in J.R.R. Tolkien’s The Lord of the Rings is “Mellon.”
The Doors of Durin form the western entrance to Moria, the ancient Dwarven realm beneath the Misty Mountains. Their inscription includes the instruction “Speak, friend, and enter,” but the crucial word is the Elvish term mellon, meaning “friend” in Sindarin.
Gandalf initially interprets the inscription as requiring a spoken password, yet eventually realizes that the answer is simply the word “friend.” This opens the doors and allows the Fellowship to enter Moria. The scene demonstrates Tolkien’s interest in philology: solving the puzzle depends on understanding the meaning and grammar of an invented language.