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former; ex-; past; one-time
earlier times; the past; previous state
formerly; previously; originally; before
「故」 has other readings with different meanings.
故あって詳しいことは今は言えない。
For certain reasons, I cannot say the details.
故なくして罰を受けることはない。
One does not receive punishment without cause.
何の故か分からず不安な気持ちになった。
I became anxious not knowing the reason.