Languages branch from one another, so one language can have many off-spring. There are several larger families that lead to smaller and smaller families that lead out to the languages still surviving today and some estimate that there are 6,900 languages still alive today
Languages can change based on patterned shifts in sounds (phonological changes), based on changes in sentence structure (syntactic changes), and based on the addition of new words, whether borrowed from other languages or created by that language (e.g. to text someone). All of these changes have occurred at some point in the past to make Urdu the language it is today.
Urdu was structurally similar to Delhis Hindustani dialect but it contained a great deal of Persian and Turkic vocabulary along with some words of Arabic origin. Another difference is that Urdu is written in the Arabic alphabet instead of in the Indian Devanagari alphabet. Standardization of the Urdu language took place during the late nineteenth and early twentieth century. During this period the formal forms of Urdu and Hindi began to diverge. Hindi was considered the language of Hindus. Words of Persian, Turkic or Arabic origin were deliberately removed from the language. Words from Sanskrit, the language of ancient Hindu religious texts, were added. Urdu, on the other hand, came to be considered a Muslim language. Urdu borrowed more heavily on Persian and Arabic and attempts were made to minimize Sanskrit influences. The political division between the two countries helped to facilitate further divergence between formal and literary Urdu and Hindi. Everyday spoken Urdu and Hindi, however, are intelligible with one another.
The development of formal Urdu and Hindi as separate languages was carried out deliberately in the nineteenth century as part of attempts by Muslims and Hindus to emphasize their distinct identities. The architects of formal Urdu deliberately adopted more Persian and Arabic words. The architects of Hindi on the other hand, tried to purge the Persian, Turkic and Arabic words that had entered everyday Hindustani speech as a result of centuries of contact with people who spoke these languages. The political division of Pakistan and India has helped to facilitate the development of separate literature and formal linguistic rules for Urdu and Hindi. In everyday speech, however, Urdu and Hindi still resemble each other so closely that some argue that they are a single language.
Source of this post :
The origins of the Urdu language - by Jerome Carter - Helium