An adverb meaning 'again and again' or 'repeatedly', often emphasizing repeated attempts or occurrences.
彼は再三注意されたのに行動を改めなかった。
He was warned repeatedly but did not change his behavior.
再三にわたる交渉の末、合意に達した。
After repeated negotiations, they reached an agreement.
再三お願いしたが対応してもらえなかった。
I asked repeatedly, but they did not respond.