There were many similarities between Khuzdul and the native tongues of Men of the Far-East of Middle-earth. This is because in the early days of Middle-earth, Men of these regions had friendly contact with the Dwarves, who were not unwilling to teach their own tongue to Men with whom they had special friendship, but Men found it difficult and were slow to learn more than isolated words, many of which they adapted and took into their own language. Adûnaic, the language of Númenor, retained some Khuzdul influences and was said to have been influenced by Khuzdul's basic structure.