Hindi and Urdu are sister languages from South Asia, spoken and understood across much of the northern part of the subcontinent from Pakistan to eastern India. The sentence 'We live in Delhi and we speak both Hindi and Urdu' might be expressed like this in the shared language:
ham dillī mẽ rahte haĩ aur hamẽ hindī aur urdū donõ ātī haĩ.

Hindi and Urdu also differ in their formal vocabulary, which they take from two different sources. Consider formal English — it uses many Latinate words, such as the ones italicized here: 'In order to comprehend this important issue we must analyse numerous different perspectives.' Hindi equivalents of these italicized words would be drawn from Sanskrit, while Urdu equivalents would be drawn from Persian and Arabic; thus formal Hindi and formal Urdu are effectively two very different languages.
The modern languages of northern South Asia are the descendants of Sanskrit, further enriched by loanwords from other languages such as Persian, Portuguese and English that have entered the subcontinent with migrants, traders and invaders during the long history of the area. Because Sanskrit is a cousin of Latin and Greek — the classical languages of Europe — Hindi and Urdu are distant relatives of modern European languages. We see this connection clearly in such Hindi-Urdu words as naam 'name', daant 'tooth' (think of 'dentist', or French 'dant'), das 'ten' (think of 'decimal') and kat 'cut'.
In many respects, the grammar of Hindi and Urdu resembles that of its distant cousin English: for example, it has a similar range of tenses and a similar assortment of formal and informal styles. Other characteristics are less familiar: all nouns have gender (masculine and feminine), and when addressing someone in Hindi-Urdu we must select pronouns and verb forms that reflect our relationship with that person, whether formal, familiar, or intimate. Thus the learner will find some features of the language to be familiar, while others will be more challenging — and perhaps more interesting also! Mother-tongue speakers of Hindi and Urdu are rightly proud of their cultural heritage, and learners of the languages will themselves be greatly enriched by the encounter with this supremely expressive and articulate pair of languages.