Early forms of present-day Hindustani developed from the Middle Indo-Aryan apabhraṃśa vernaculars of present-day North India in the 7th–13th centuries. Hindustani emerged as a contact language around the Ganges-Yamuna Doab (Delhi, Meerut and Saharanpur), a result of the increasing linguistic diversity that occurred during the Muslim period in the Indian subcontinent. Amir Khusrow, who lived in the thirteenth century during the Delhi Sultanate period in North India, used these forms (which was the lingua franca of the period) in his writings and referred to it as Hindavi (Persian: ھندوی, lit. 'of Hindus or Indians'). By the end of the century, the military exploits of Alauddin Khalji, introduced the language in the Deccan region, which led to the development of its southern dialect Deccani, which was promoted by Muslim rulers in the Deccan. The Delhi Sultanate, which comprised several Turkic and Afghan dynasties that ruled much of the subcontinent from Delhi, was succeeded by the Mughal Empire in 1526 and preceded by the Ghorid dynasty and Ghaznavid Empire before that.

Ancestors of the language were known as Hindui, Hindavi, Zabān-e Hind (transl. 'Language of India'), Zabān-e Hindustan (transl. 'Language of Hindustan'), Hindustan ki boli (transl. 'Language of Hindustan'), Rekhta, and Hindi. Its regional dialects became known as Zabān-e Dakhani in southern India, Zabān-e Gujari (transl. 'Language of Gujars') in Gujarat, and as Zabān-e Dehlavi or Urdu around Delhi. It is an Indo-Aryan language, deriving its base from the Western Hindi dialect of the Ganges-Yamuna Doab (Delhi, Meerut and Saharanpur) known as Khariboli—the contemporary form being classed under the umbrella of Old Hindi.

Although the Mughals were of Timurid (Gurkānī) Turco-Mongol descent, they were Persianised, and Persian had gradually become the state language of the Mughal empire after Babur. Mughal patronage led to a continuation and reinforcement of Persian by Central Asian Turkic rulers in the Indian Subcontinent, since Persian was also patronized by the earlier Turko-Afghan Delhi Sultanate who laid the basis for the introduction and use of Persian in the subcontinent.

Hindustani began to take shape as a Persianised vernacular during the Delhi Sultanate (1206–1526 AD) and Mughal Empire (1526–1858 AD) in South Asia. Hindustani retained the grammar, as well as the core Sanskritic and Prakritic vocabulary, of the local Indian language of the Ganges-Yamuna Doab called Khariboli. However, as an emerging common dialect, Hindustani absorbed large numbers of Persian, Arabic, and Turkic loanwords, and as Mughal conquests grew it spread as a lingua franca across much of northern India; this was a result of the contact of Hindu and Muslim cultures in Hindustan that created a composite Ganga-Jamuni tehzeeb. The language was also known as Rekhta, or 'mixed', which implies that the Sanskritic and Prakritic vocabulary base of Old Hindi was mixed with Persian loanwords. Written in the Perso-Arabic, Devanagari, and occasionally Kaithi or Gurmukhi scripts, it remained the primary lingua franca of northern India for the next four centuries, although it varied significantly in vocabulary depending on the local language. Alongside Persian, it achieved the status of a literary language in Muslim courts and was also used for literary purposes in various other settings such as Sufi, Nirgun Sant, Krishna Bhakta circles, and Rajput Hindu courts. Its majors centres of development incl…

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At the spoken level, Hindi and Urdu are considered registers of a single language, Hindustani or Hindi–Urdu, as they share a common grammar and core vocabulary, they differ in literary and formal vocabulary; where literary Hindi draws heavily on Sanskrit and to a lesser extent Prakrit, literary Urdu draws heavily on Persian and Arabic loanwords. The grammar and base vocabulary (most pronouns, verbs, adpositions, etc.) of both Hindi and Urdu, however, are the same and derive from a Prakritic base, and both have Persian/Arabic influence.

The standardised registers Hindi and Urdu are collectively known as Hindi–Urdu. Hindustani is the lingua franca of the north and west of the Indian subcontinent, though it is understood fairly well in other regions also, especially in the urban areas. This has led it to be characterised as a continuum that ranges between Hindi and Urdu. A common vernacular sharing characteristics with Sanskritised Hindi, regional Hindi and Urdu, Hindustani is more commonly used as a vernacular than highly Sanskritised Hindi or highly Persianised Urdu.

This can be seen in the popular culture of Bollywood or, more generally, the vernacular of North Indians and Pakistanis, which generally employs a lexicon common to both Hindi and Urdu speakers. Minor subtleties in region will also affect the 'brand' of Hindustani, sometimes pushing the Hindustani closer to Urdu or to Hindi. One might reasonably assume that the Hindustani spoken in Lucknow, Uttar Pradesh (known for its usage of Urdu) and Varanasi (a holy city for Hindus and thus using highly Sanskritised Hindi) is somewhat different.
Standard Hindi, one of the 22 officially recognized languages of India and the official language of the Union, is usually written in the indigenous Devanagari script of India and exhibits less Persian and Arabic influence than Urdu. It has a literature of 500 years, with prose, poetry, religion and philosophy. One could conceive of a wide spectrum of dialects and registers, with the highly Persianised Urdu at one end of the spectrum and a heavily Sanskritised variety spoken in the region around Varanasi, at the other end. In common usage in India, the term Hindi includes all these dialects except those at the Urdu spectrum. Thus, the different meanings of the word Hindi include, among others:
199 standardized Hindi as taught in schools throughout India (except some states such as Tamil Nadu),
299 formal or official Hindi advocated by Purushottam Das Tandon and as instituted by the post-independence Indian government, heavily influenced by Sanskrit,
399 the vernacular dialects of Hindustani as spoken throughout India,
499 the neutralized form of Hindustani used in popular television and films (which is nearly identical to colloquial Urdu), or

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Before 1947, Hindustani was officially recognised by the British Raj. In the post-independence period however, the term Hindustani has lost currency and is not given any official recognition by the Indian or Pakistani governments. The language is instead recognised by its standard forms, Hindi and Urdu.
Hindi is declared by Article 343(1), Part 17 of the Indian Constitution as the "official language (राजभाषा, rājabhāṣā) of the Union." (In this context, "Union" means the Federal Government and not the entire country —India has 23 official languages.) At the same time, however, the definitive text of federal laws is officially the English text and proceedings in the higher appellate courts must be conducted in English.

At the state level, Hindi is one of the official languages in 10 of the 29 Indian states and three Union Territories, respectively: Bihar, Chhattisgarh, Haryana, Himachal Pradesh, Jharkhand, Madhya Pradesh, Rajasthan, Uttarakhand, Uttar Pradesh and West Bengal; Andaman and Nicobar Islands, Dadra and Nagar Haveli, and Delhi.

In the remaining states, Hindi is not an official language. In states like Tamil Nadu and Karnataka, studying Hindi is not compulsory in the state curriculum. However, an option to take the same as second or third language does exist. In many other states, studying Hindi is usually compulsory in the school curriculum as a third language (the first two languages being the state's official language and English), though the intensiveness of Hindi in the curriculum varies.
Urdu is the national language (قومی زبان, qaumi zabān) of Pakistan, where it shares official language status with English. Although English is spoken by many, and Punjabi is the native language of the majority of the population, Urdu is the lingua franca. In India, Urdu is one of the languages recognised in the Eighth Schedule to the Constitution of India and is an official language of the Indian states of Jharkhand, Bihar, Telangana, Uttar Pradesh, West Bengal, and also the Union Territories of Delhi and Jammu and Kashmir. Although the government school system in most other states emphasises Standard Hindi, at universities in cities such as Lucknow, Aligarh and Hyderabad, Urdu is spoken and learnt, and Saaf or Khaalis Urdu is treated with just as much respect as Shuddh Hindi.