This number includes speakers of the Pamiri languages, including Wakhi and Shughni, and the Yaghnobi people who in the past were considered by the government of the Soviet Union nationalities separate from the Tajiks.In the 19 Soviet censuses, the Yaghnobis and Pamiri language speakers were counted as separate nationalities.By the eleventh century (Yusof Ḵāṣṣ-ḥājeb, Qutadḡu bilig, lines 280, 282, 3265), the Qarakhanid Turks applied this term more specifically to the Persian Muslims in the Oxus basin and Khorasan, who were variously the Turks’ rivals, models, overlords (under the Samanid Dynasty), and subjects (from Ghaznavid times on). The distinction between Turk and Tajik became stereotyped to express the symbiosis and rivalry of the (ideally) nomadic military executive and the urban civil bureaucracy (Niẓām al-Molk: tāzik, pp. Tajiks are a substantial minority in Uzbekistan, as well as in overseas communities.
According to Richard Nelson Frye, a leading historian of Iranian and Central Asian history, the Persian migration to Central Asia may be considered the beginning of the modern Tajik nation, and ethnic Persians, along with some elements of East-Iranian Bactrians and Sogdians, as the main ancestors of modern Tajiks.
In later works, Frye expands on the complexity of the historical origins of the Tajiks.
The dialects of the Persians of Iran and of the Tajiks of central Asia have a common origin.
Russian is widely used in government and business in Tajikistan as well.
For example, the Tajiks of China are actually Pamiris and speak the Eastern Iranian Pamiri languages and are distinct from more western Tajiks.
The Tajiks are an Iranian people, speaking a variety of Persian, concentrated in the Oxus Basin, the Farḡāna valley (Tajikistan and parts of Uzbekistan) and on both banks of the upper Oxus, i.e., the Pamir Mountains (Mountain Badaḵšān, in Tajikistan) and northeastern Afghanistan (Badaḵšān and Kābol)..
In a 1996 publication, Frye explains that many "factors must be taken into account in explaining the evolution of the peoples whose remnants are the Tajiks in Central Asia" and that "the peoples of Central Asia, whether Iranian or Turkic speaking, have one culture, one religion, one set of social values and traditions with only language separating them." The most plausible and generally accepted origin of the word is Middle Persian tāzīk ‘Arab’ (cf.
New Persian tāzi), or an Iranian (Sogdian or Parthian) cognate word.
~45% of Tajik men share R1a (M17), ~18% J (M172), and ~8% R2 (M124).