Central Asia or Middle Asia is the core region of the Asian continent and 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 six countries generally considered to be within the region all have names ending with the Persian suffix "-stan", meaning "land of") and is within the scope of the wider Eurasian continent. In modern contexts, all definitions of Central Asia include these five republics of the former Soviet Union: Kazakhstan (pop. 17 million), Kyrgyzstan (6 million), Tajikistan (8 million), Turkmenistan (5 million) and Uzbekistan (30 million), for a total population of about 66 million. Afghanistan (pop. 31 million) is also sometimes included.