Kazakhstan is a country of Central Asia. It is bounded on the northwest and north by Russia , on the east by China , and on the south by Kyrgyzstan , Uzbekistan , the Aral Sea, and Turkmenistan ; the Caspian Sea bounds Kazakhstan to the southwest. Kazakhstan is the largest country in Central Asia and the ninth-largest in the world. The capital is Nursultan (formerly Astana, Aqmola, and Tselinograd), in the north-central part of the country. Kazakhstan, formerly a constituent (union) republic of the U.S.S.R., declared independence on December 16, 1991 . Kazakhstan’s climate is sharply continental, and hot summers alternate with equally extreme winters, especially in the plains and valleys. Kazakhs speak a Turkic language of the Northwest or Kipchak (Qipchaq) group. Russian, an official language , functions widely alongside Kazakh , which is the state language . Russian is the most widely understood language in the country. Kazakhstan is a member of theShanghai Cooperation Organization (SCO) .