The character originally represented a flexed arm and it's fairly easy to see why. Common uses for this Kanji character would be in phrases such as - "He's Strong" - She posessses great power or influence" - He's making great effort toward that goal", etc.
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As with most Japanese Symbols, they are routinely conbined with other Kanji to create new compounds. Ideas such as "violence", "cooperation", "masterpiece" and even "sumo wrestler" are all constructed using the Japanese power symbol, chikara.

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