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as soon as; no sooner than; one way or another
objection
彼は家に着くや否や寝た。
As soon as he arrived home, he fell asleep.
店が開くや否や、客が押し寄せた。
As soon as the store opened, customers rushed in.
彼女はその手紙を見るや否や、泣き出した。
The moment she saw the letter, she burst into tears.