Khuzdul is the language Tolkien created for the Dwarves of Middle-earth.
In Tolkien’s legendarium, the Dwarves keep Khuzdul secret from outsiders. It is described as a language taught to them by Aulë, the Vala who created the Dwarves. Because of this secrecy, Tolkien presents relatively little of Khuzdul compared with the more extensively developed Elvish languages.
The best-known Khuzdul expression is “Baruk Khazâd! Khazâd ai-mênu!”, associated with Dwarven battle cries. Place-names such as Khazad-dûm also reveal elements of the language. Khuzdul has a sound and structure distinct from Quenya and Sindarin, the better-known languages associated with the Elves.
A frequent mix-up is to identify any Tolkien language as Elvish. Quenya is commonly called High-elven, Sindarin is a major language of the Grey-elves, and Adûnaic is associated with Númenor. Khuzdul is specifically the Dwarves’ language, and its limited surviving vocabulary reflects Tolkien’s portrayal of Dwarven cultural privacy.