Hindustani was the native language spoken in northern India (what is historically known as the region of Hindustan), and it belongs to the Western Hindi language class of Central Indo-Aryan languages. Mughal rulers brought with them to India the Persian language. In cities such as Delhi, Hindustani began to acquire some Persian loanwords and continued to be called "Hindi" as well as "Urdu". While Urdu retained the grammar and core vocabulary of the local Delhi dialect, it adopted the Nastaleeq writing system.