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consequence; outcome; result; blame; fault
寝不足のせいで頭がぼんやりしている。
My head is foggy due to lack of sleep.
天気のせいで試合が中止になった。
The game was canceled because of the weather.
年のせいか最近階段がつらくなってきた。
Maybe it's my age, but stairs have been getting harder.