It is closely related to neighbouring Dari of Afghanistan with which it forms a continuum of mutually intelligible varieties of the Persian language.

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.

[21] Two major cities of Central Asia, Samarkand and Bukhara, are in present-day Uzbekistan, but are defined by a prominent native usage of Tajik language.

[citation needed] This Tajik–Uzbek bilingualism has had a strong influence on the phonology, morphology, and syntax of Bukharan Tajik.

[24] Tajiks are also found in large numbers in the Surxondaryo Region in the south and along Uzbekistan's eastern border with Tajikistan.

[25] Official statistics in Uzbekistan state that the Tajik community comprises 5% of the nation's total population.

[26] However, these numbers do not include ethnic Tajiks who, for a variety of reasons, choose to identify themselves as Uzbeks in population census forms.

[30] 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.

A very important moment in the development of the contemporary Tajik, especially of the spoken language, is the tendency in changing its dialectal orientation.

When a noun is used as a direct object, it is marked by the suffix -ро -ro, e.g., Рустамро задам Rustam-ro zadam 'I hit Rustam'.

[34] Tajik is conservative in its vocabulary, retaining numerous terms that have long since fallen into disuse in Iran and Afghanistan, such as арзиз arziz 'tin' and фарбеҳ farbeh 'fat'.

Most modern loan words in Tajik come from Russian as a result of the position of Tajikistan within the Soviet Union.

Since the late 1980s, an effort has been made to replace loanwords with native equivalents, using either old terms that had fallen out of use or coined terminology (including from Iranian Persian).

Many of the coined terms for modern items such as гармкунак garmkunak 'heater' and чангкашак čangkašak 'vacuum cleaner' differ from their Afghan and Iranian equivalents, adding to the difficulty in intelligibility between Tajik and other forms of Persian.

In the 9th century AD, following the rise of the Samanids, whose state was centered around the cities of Bukhoro (Buxoro), Samarqand and Herat and covered much of Uzbekistan, Tajikistan, Afghanistan and northeastern Iran, New Persian emerged as the court language and swiftly displaced Arabic.

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.

Once spoken in areas of Turkmenistan, such as Merv, Tajik is today virtually non-existent in that country.

[48] Nevertheless, Tajik persisted in pockets, notably in Samarqand, Bukhoro and Surxondaryo Region, as well as in much of what is today Tajikistan.

The influence of this influx of ethnic Tajik immigrants from the Uzbek SSR 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.

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.

Increasing contact with media from Iran and Afghanistan, after decades of isolation under the Soviets, as well as governmental orientation toward a "Persianisation" of the language have brought closer Tajik and the other Persian dialects.