Central Asia stretches from the Caspian Sea in the west to China in the east and from Afghanistan in the south to Russia in the north. The region consists of the former Soviet republics of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. It is also colloquially referred to as "the stans" as the countries generally considered to be within the region all have names ending with the Persian suffix "-stan", meaning "land of".
Central Asia has a population of about 105 million, consisting of five republics: Kazakhstan (pop. 18 million), Kyrgyzstan (6 million), Tajikistan (9 million), Turkmenistan (6 million), and Uzbekistan (31 million). Afghanistan (pop. 35 million), which is a part of South Asia, is also sometimes included in Central Asia.
Central Asia has historically been closely tied to its nomadic peoples and the Silk Road. It has acted as a crossroads for the movement of people, goods, and ideas between Europe, Western Asia, South Asia, and East Asia. The Silk Road connected Muslim lands with the people of Europe, India, and China. This crossroads position has intensified the conflict between tribalism and traditionalism and modernization.
In pre-Islamic and early Islamic times, Central Asia was predominantly Iranian, populated by Eastern Iranian-speaking Bactrians, Sogdians, Chorasmians and the semi-nomadic Scythians and Parthians. After expansion by Turkic peoples, Central Asia also became the homeland for the Kazakhs, Uzbeks, Tatars, Turkmen, Kyrgyz, and Uyghurs; Turkic languages largely replaced the Iranian languages spoken in the area.
From the mid-19th century until almost the end of the 20th century, most of Central Asia was part of the Russian Empire and later the Soviet Union, both Slavic-majority countries, and the five former Soviet "-stans" are still home to about 7 million ethnic Russians and 500,000 Ukrainians.
The idea of Central Asia as a distinct region of the world was introduced in 1843 by the geographer Alexander von Humboldt. The borders of Central Asia are subject to multiple definitions. Historically built political geography and geoculture are two significant parameters widely used in the scholarly literature about the definitions of the Central Asia.
The most limited definition was the official one of the Soviet Union, which defined Middle Asia as consisting solely of Uzbekistan, Turkmenistan, Tajikistan and Kyrgyzstan. This definition was also often used outside the USSR during this period.