Tajik is an Indo-European language closely linked to Persian and Dari, and hence these three languages have a shared literary heritage. Unlike most central Asian languages, it is not related to Turkish. From the 9th century Tajik was written in a modified version of the Perso-Arabic script (it had previously been written in Sogdian), and the Arab invasions of this time account for its Arabic loan words. It was only with Stalin's division of central Asia in the 1920s that Tajik began to be seen as a linguistic entity distinct from Persian.
Historically Tajiks called their language Zaban-e`-Pa-rsi-, meaning "Persian language"; the term zabani tajiki-, or "Tajik language", was introduced in the 20th century by the Soviets. Most speakers of Tajik live in Tajikistan and Uzbekistan. Tajik is the official language of Tajikistan. In Afghanistan, where Tajiks make up a large part of the population, the dialect is less influenced by Turkic languages and is called Dari.
The dialect has diverged from Persian as spoken in Afghanistan and Iran, as a result of political borders, geographical isolation, the standardization process, and the influence of Russian and neighboring Turkic languages. The standard language is based on the north-western dialects of Tajik (region of old major city of Samarkand), which have been somewhat influenced by the neighboring Uzbek language as a result of geographical proximity. Tajik also retains numerous archaic elements in its vocabulary, pronunciation, and grammar that have been lost elsewhere in the Persophone world, in part due to its relative isolation in the mountains of Central Asia.
Tajik was designated as the state language of the Tajik SSR in 1929. For the first decade it was written in a modified Latin script, but in 1939 it was again replaced, this time by Cyrillic. Over the course of the 20th century Tajik has acquired a significant amount of Russian vocabulary, in particular technical terms for which there is no immediately obvious Persian root.
Today an estimated two-thirds of Tajikistan's population speak Tajik as their mother tongue and it is the main language of education.
The most important historically Tajik/Persian-speaking cities of Central Asia, Samarqand and Bukhara, are in present-day Uzbekistan. In Uzbekistan Tajiks are the largest part of the population of the ancient cities of Bukhara and Samarqand, and are found in large numbers in the Surxondaryo Province in the south and along Uzbekistan's eastern border with Tajikistan.
Official statistics in Uzbekistan state that the Tajik community comprises 5% of the nation's total population. However, these numbers do not include ethnic Tajiks who, for a variety of reasons, choose to identify themselves as Uzbeks in population census forms. During the Soviet "Uzbekization" supervised by Sharof Rashidov, the head of the Uzbek Communist Party, Tajiks had to choose either to stay in Uzbekistan and get registered as Uzbek in their passports or leave the republic for the less developed agricultural and mountainous Tajikistan. Subjective expert estimates suggest that Tajiks may make up 15 to 25 percent of Uzbekistan's population.
Tajiks constitute 80% of Tajikistan's population, and Persian dominates in most parts of the country. Some Tajiks in Badakhshan in southeastern Tajikistan, where the Pamiri languages are the native languages of most residents, are bilingual-speakers. Tajiks are the dominant ethnic group in Northern Afghanistan as well, and are also the majority group in scattered pockets elsewhere in the country, particularly urban areas such as Kabul, Mazar, Kunduz, Ghazni and Herat. Tajiks constitute between 25% and 30% of the total population of the country. In Afghanistan, the dialects spoken by ethnic Tajiks are written using the Perso-Arabic script and referred to as Dari, along with the Persian dialects of other groups in Afghanistan such as the Hazara and Aimaq. 50% of Afghan citizens are native speakers of Dari. A large Tajik-speaking diaspora exists due to the instability that has plagued Central Asia in recent years, with significant numbers of Tajiks found in Russia, Kazakhstan, and beyond.
Tajik dialects can be approximately split into the following groups:
Northern dialects (Northern Tajikistan, southern parts of Uzbekistan and Kyrgyzstan).
Central dialects (dialects of Mastchoh, Aini, Hissor and, parts of Varzob).
Southern dialects (dialects of Qarotegin, Kulob, dialects of Badakhshan, etc.)
Southeastern dialects (dialects of Vanj and Darvoz).
The dialects used among the native Bukharian Jews of Central Asia are known as Bukhori, and belong to the northern dialect grouping. They are chiefly distinguished by the inclusion of Hebrew terms, principally religious vocabulary, and a historical use of the Hebrew alphabet. Despite these differences, Bukhori is readily intelligible to other Tajik-speakers, particularly speakers of northern dialects.
According to many scholars, the New Persian language (which subsequently evolved into the Persian forms spoken in Iran, Afghanistan and Tajikistan) developed in Transoxiana and Khorasan, in what are today parts of Afghanistan, Iran, Uzbekistan and Tajikistan. While the New Persian language was descended primarily from Middle Persian, it also incorporated substantial elements of other Iranian languages of ancient Central Asia, such as Sogdian.
Following the Arab conquest of Iran and most of Central Asia in the 8th century AD, Arabic for a time became the court language, and Persian and other Iranian languages were relegated to the private sphere. In the 9th century AD, following the rise of the Samanids, whose state covered much of Uzbekistan, Tajikistan, Afghanistan and northeastern Iran and was centered around the cities of Bukhoro (Bukhara), Samarqand and Herat, New Persian emerged as the court language and swiftly displaced Arabic. Arabic influence continued to show itself in the form of the Perso-Arabic script used to write the language (replaced in Tajik by Latin and then Cyrillic in the 20th century) and a large number of Arabic loanwords.
New Persian became the lingua franca of Central Asia for centuries, although it eventually lost ground to the Chaghatai language in much of its former domains as a growing number of Turkic tribes moved into the region from the east. Since the 16th century AD, Tajiki has come under increasing pressure from neighboring Turkic languages, particularly Uzbek, which has largely replaced it in most areas of what is now Uzbekistan. Once spoken in areas of Turkmenistan, such as Merv, Tajik is today virtually non-existent in that country. Nevertheless, Tajik persisted in pockets of what is now Uzbekistan, notably in Samarqand, Bukhoro and Surxondaryo Province, as well as in much of what is today Tajikistan.
The creation of the Tajik Soviet Socialist Republic within the Soviet Union in 1929 helped to safeguard the future of Tajik, as it became an official language of the republic alongside Russian. Still, substantial numbers of Tajik-speakers remained outside the borders of the republic, mostly in the neighboring Uzbek Soviet Socialist Republic, which created a source of tension between Tajiks and Uzbeks. Neither Samarqand nor Bukhoro was included in the nascent Tajik S.S.R., despite their immense historical importance in Tajik history. After the creation of the Tajik S.S.R., a large number of ethnic Tajiks from the Uzbek S.S.R. migrated there, particularly to the region of the capital, Dushanbe, exercising a substantial influence in the republic's political, cultural and economic life. The influence of this influx of ethnic Tajik immigrants from the Uzbek S.S.R. is most prominently manifested in the fact that literary Tajik is based on their northwestern dialects of the language, rather than the central dialects that are spoken by the natives in the Dushanbe region and adjacent areas.
After the fall of the Soviet Union and Tajikistan's independence in 1991, the government of Tajikistan has made substantial efforts to promote the use of Tajik in all spheres of public and private life. Tajik is gaining ground among the once-Russified upper classes, and continues its role as the vernacular of the majority of the country's population. There has been a rise in the number of Tajik publications. Increasing contact with media from Iran and Afghanistan, after decades of isolation under the Soviets, is also having an effect on the development of the language. In 2009, Tajikistan adopted a law that removes Russian as the "language for interethnic communication.