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alternately; in succession
希望と絶望が交々に訪れる厳しい日々だ。
These are tough days where hope and despair visit alternately.
春と冬の気候が交々に現れる季節だった。
It was a season where spring and winter weather alternated.
成功と失敗を交々に繰り返して成長する。
You grow by alternating between success and failure.