Khanate is often used in a historical context, especially when studying regions once ruled by khans. The Golden Horde was a Mongol and later Turkicized khanate that controlled parts of Eastern Europe.
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Not Modern
'Khanate' is archaic, it's not used for contemporary political entities but for historic states. Today, what used to be the Kazan Khanate is part of Russia.
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Mongol Empire
Khanates were common during the Mongol Empire, it's helpful to connect this term with Mongolian history. After Genghis Khan's death, the Mongol Empire was divided into several khanates.