The Dari language
 
Group Iranian (with Kurdish, Talysh etc.), Southwest Iranian (with Tadjik, Tati etc.)
Geography Dari is spoken and written by natives in central and northern Afghanistan and all over the country by the urban population. Since the Middle Ages Dari (or Farsi Kabuli, another name for it) has been widely used as the language of the educated classes of people. The total number of its speakers makes some 4 million people, including several minor groups of autochtonic population of the region (e.g. Khazareans, a Turkish people living in Afghanistan). Dari includes various dialects, and the literature language is formed by the one of Kabul. 
History Dari, Persian and Tadjik languages all come from one source (Classical Persian), but historically the territory of modern Afghanistan was included in the region where some peculiarities in comparison with the literature Persian appeared, so that's how Dari now differs more from Persian than from Tadjik. Dari became an independent tongue in the 16th century. It used to be very conservative, and the language of aristocracy in the beginning of the 20th century was sometimes not understandable for ordinary people. After Afghanistan was proclaimed a republic (1973), the popular language became more important in social life, and literature forms have changed a little. 
Phonetics Dari has got two long vowels [o] and [e], which Persian lacks, and uses two archaic diphthongs, ai and aw
Nominal Morphology Dari grammar has a complicated system of aspects and tenses of the verb. 
Lexicon The vocabulary differs much from Persian and is closer to Tadjik. 
Writing Arabic based script
Close Contacts Tadjik, Persian are the closest relatives; Pashto and Baluchi are the closest neighbours.
Sample  
Picture Gazni Mausoleum in Afghanistan
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