Hindi (Devanagari: हिन्दी, IAST: Hindī), or Modern Standard Hindi (Devanagari: मानक हिन्दी, IAST: Mānak Hindī) is a standardised and Sanskritised register of the Hindustani language. Along with the English language, Hindi written in the Devanagari script is the official language of India.
On 14 September 1949, the Constituent Assembly of India adopted Hindi written in Devanagari script as the official language of the Republic of India. To this end, several stalwarts rallied and lobbied pan-India in favor of Hindi, most notably Beohar Rajendra Simha along with Hazari Prasad Dwivedi, Kaka Kalelkar, Maithili Sharan Gupt and Seth Govind Das who even debated in Parliament on this issue. As such, on the 50th birthday of Beohar Rajendra Simha on 14 September 1949, the efforts came to fruition following adoption of Hindi as the official language. It is one of the 22 scheduled languages of the Republic of India. However, it is not the national language of India because no language was given such a status in the Indian constitution.
Hindi is the lingua franca of the Hindi belt, and to a lesser extent the whole of India (usually in a simplified or pidginized variety such as Bazaar Hindustani or Haflong Hindi). Outside India, several other languages are recognized officially as "Hindi" but do not refer to the Standard Hindi language described here and instead descend from other dialects of Hindustani, such as Awadhi and Bhojpuri. Such languages include Fiji Hindi, which is official in Fiji, and Caribbean Hindustani, which is a recognized language in Trinidad and Tobago, Guyana, and Suriname. Apart from specialized vocabulary, Hindi is mutually intelligible with Standard Urdu, another recognized register of Hindustani.
Individually, as a linguistic variety, Hindi is the fourth most-spoken first language in the world, after Mandarin, Spanish and English. Alongside Urdu as Hindustani, it is the third most-spoken language in the world, after Mandarin and English.
The term Hindī originally was used to refer to inhabitants of the region east of the Indus. It was borrowed from Classical Persian Hindī (Iranian Persian Hendi), meaning "Indian", from the proper noun Hind "India".