Urdu
Hindi, also historically known as Hindui (हिंदुई), is the most spoken language of India, which replaces much of Urdu's Farsi, Chagatai and Arabic terminology with Sanskrit derived vocabulary. They are grammatically the same. Everyday words are often shared between the two registers, while formal vocabulary can differ significantly. Urdu and Hindi speakers can understand each other with little to no difficulty, largely from using shared, or English vocabulary, rather than using highly Arabized or Sanskritized vocabulary. Hindi speakers are more likely to use words of Arabic/Persian origin (Kitaab, Dil, Mahobbat), than Urdu speakers are to use words of Sanskrit origin (Pustak, Man, Prem), as Urdu-speaking Pakistani's have less exposure to Hindi, than Hindi-speaking Indians do to Urdu. This can be seen in Bollywoods extensive use of the Urdu register, and India being a nation where both registers are natively spoken.