imperial domain, world
寰 centers on a vast enclosed realm: the imperial domain or the whole world, conceived as a bounded territory under one rule.
寰 combines 宀 (roof) with 睘, a component associated with encircling or surrounding. Together they suggest a domain enclosed under one roof, extending to the imperial realm or the world.
Under a roof 宀, the encircling shape 睘 suggests a walled territory. Picture the emperor's palace roof covering the entire world within its walls.
For カン, imagine a great khan ruling the imperial domain from under the roof: khan -> カン, and the whole world is his realm.
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