Hindustani is an Indo-Aryan language spoken in Deccan, Northern India and Pakistan, and used as a lingua franca in both countries. Hindustani is a pluricentric language with two standard registers, known as Hindi and Urdu. Thus, it is also called Hindi–Urdu. Colloquial registers of the language fall on a spectrum between these standards. In modern times, a third variety of Hindustani with significant English influences has also appeared which is sometimes called Hinglish or Urdish.

The Indo-Aryan languages are a branch of the Indo-Iranian languages in the Indo-European language family. As of the early 21st century, they have more than 800 million speakers, primarily concentrated in Bangladesh, India, Pakistan, Sri Lanka, Maldives and Nepal. Moreover, apart from the Indian subcontinent, large immigrant and expatriate Indo-Aryan–speaking communities live in Northwestern Europe, Western Asia, North America, the Caribbean, Southeast Africa, Polynesia and Australia, along with several million speakers of Romani languages primarily concentrated in Southeastern Europe. There are over 200 known Indo-Aryan languages.