Dari refers to a modern Persian dialect that is the standard language used in administration, government, radio, television, and print media in Afghanistan, in part of Iran, and in Tajikistan. Because of the preponderance of speakers in contemporary Afghanistan, it is also known as Afghan Persian in some Western sources. It is the term officially recognized and promoted in 1964 by the Afghan government for the Persian language. As defined in the Constitution of Afghanistan, it is one of the two official languages of Afghanistan; the other is Pashto. Dari is the most widely spoken language in Afghanistan and the native language of approximately 50% of the population, serving as the country's lingua franca. The Iranian and Afghan dialects of Persian are highly mutually intelligible, with differences found primarily in the vocabulary and phonology. But in historical usage, Dari refers to the Middle Persian court language of the Sassanids. Wikipedia