再三 (zàisān) or means "repeatedly" or "time and again" in a formal way, and is usually placed before a two-syllable verb.

老师再三强调这次考试对我们很重要。The teacher has stressed over and over that this exam is really important for us.
中国政府再三警告美国不要干涉中国的内政。China's government warns the USA repeatedly not to interfere in China's affairs.
她再三犹豫之后，选择了放弃比赛。After hesitating again and again, she chose to give up the competition.
我们再三考虑过后，决定满足你的这个要求。After back and forth considering, we decided to satisfy your requirements.
我再三提醒你出国旅游一定要小心你的钱包。I reminded you, again and again, that you need to be careful with your wallet when you travel abroad.

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Examples