The Dwarves’ language created by J.R.R. Tolkien is Khuzdul. In Tolkien’s legendarium, the Dwarves keep Khuzdul largely private and use it among themselves rather than teaching it broadly to other peoples.
Khuzdul is associated with the Dwarves of Middle-earth, including the folk of Erebor and Khazad-dûm. Tolkien designed elements of the language with a sound and structure distinct from his Elvish languages. Its secrecy is part of the Dwarves’ cultural identity, and even their personal names used in dealings with outsiders are often not their true Khuzdul names.
Khuzdul is commonly confused with Quenya or Sindarin, which are Elvish languages. Adûnaic, meanwhile, is the language of the Men of Númenor. Tolkien developed much more extensive material for some languages than for Khuzdul, so surviving examples of Khuzdul are comparatively limited.