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. 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's five former Soviet republics are Kazakhstan (pop. 17 million), Kyrgyzstan (5.7 million), Tajikistan (8.0 million), Turkmenistan (5.2 million), and Uzbekistan (30 million), giving the region a total population of about 66 million. Although not a former Soviet republic, Afghanistan (pop. 29 million) is also sometimes included.
https://en.wikipedia.org/wiki/Central_Asia