The Sogdian language is usually assigned to a Northeastern group of the Iranian languages. No direct evidence of an earlier version of the language ("Old Sogdian") has been found, although mention of the area in the Old Persian inscriptions means that a separate and recognisable Sogdia existed at least since the Achaemenid Empire (559–323 BCE).

Like Khotanese, Sogdian possesses a more conservative grammar and morphology than Middle Persian. The modern Eastern Iranian language Yaghnobi is the descendant of a dialect of Sogdian spoken around the 8th century in Osrushana, a region to the south of Sogdia.

The economic and political importance of Sogdian guaranteed its survival in the first few centuries after the Muslim conquest of Sogdia in the early eighth century. A dialect of Sogdian spoken around the 8th century in Ustrashana (capital: Bunjikat, near present-day Istaravshan, Tajikistan), a region to the south of Sogdia, developed into Yaghnobi language and has survived into the 21st century.[8] It is spoken by the Yaghnobi people.

Discovery of Sogdian texts

The finding of manuscript fragments of the Sogdian language in China's Xinjiang region sparked the study of the Sogdian language. Robert Gauthiot, (the first Buddhist Sogdian scholar) and Paul Pelliot, (who while exploring in Dunhuang, retrieved Sogdian material) began investigating the Sogdian material that Pelliot had discovered. Gauthiot published many articles based on his work with Pelliot's material, but died during the First World War. One of Gauthiot's most impressive articles was a glossary to the Sogdian text, which he was in the process of completing when he died. This work was continued by Émile Benveniste after Gauthiot's death.[9]

Dunhuang and Turfan were the two most plentiful sites of Manichean, Buddhist, and Christian Sogdian texts. Sogdiana itself actually contained a much smaller collection of texts. These texts were business related, belonging to a minor Sogdian king, Divashtich. These business texts dated back to the time of the Muslim conquest, about 700.[10]

As in other writing systems descended from the Proto-Sinaitic script, there are no special signs for vowels. As in the parent Aramaic system, the consonantal signs ’ y w can be used as matres lectionis for the long vowels [a: i: u:] respectively. However, unlike it, these consonant signs would also sometimes serve to express the short vowels (which could also sometimes be left unexpressed, as they always are in the parent systems).[11] To distinguish long vowels from short ones, an additional aleph could be written before the sign denoting the long vowel.[11]