The three closely related languages–Modern Persian, Dari (Farsi-Kabuli) and Tajiki–form a vast continuum of dialects, stretching from western Iran to Afghanistan and Central Asia. Linguistically it is very hard to draw a geographical line or define a geographical border between the dialects of Persian proper, those of the Dari language and those of Tajiki, a line or border based on purely linguistic factors, as these dialects overlap and merge into one another. It is therefore more reasonable to conceive of these dialects as a single linguistic continuum within which groups can be defined. In R. Farhadi's book on Persian as spoken in Afghanistan, a rough classification of the whole mass of the dialects of Persian, Dari and Tajiki is suggested. According to this classification, the Persian continuum can be divided into two major groups: Western and Eastern. The former includes the Persian dialects of western and central Iran, while the latter includes the remaining dialects, namely those of eastern Iran (Khorasan and Sistan), all the Dari dialects of Afghanistan, and the Tajiki of the former Soviet Central Asia. A brief look at this classification is enough to reveal an unequal distribution of dialects between the two groups, as the Eastern group covers a geographically much vaster area than the Western. However, even this classification does not present the eastern dialects as homogenous, insofar as the Eastern group includes two subdivisions: 1) the Khorasani, which covers eastern Iran and western Afghanistan; and 2) the Afghano-Tajiki, which encompasses central and northern Afghanistan and the former Soviet Central Asia.

The purpose of the present article is to prove that the Khorasani dialects deserve a much more prominent place in the classification than that of just a sub-division, and that they form a group of their own. For their similarities to Western dialects are no less significant than their similarities to Eastern dialects. On the other hand, their peculiarities within the Persian-Dari-Tajiki continuum are of such a degree and quality as to make them equally different from both extreme groups: Western and Eastern. All these factors are enough reason for Khorasani dialects to claim an independent place or position for themselves in the classification.