Former director-general of the Bureau of Investigation Yeh

Sheng-mao issued a statement Saturday that said he had

given a verbal report to prosecutor General Chen Tsung-

ming regarding the information that the then-President 

Chen Shui-bian’s daughter-in-law had opened bank accounts

overseas.

前調查局長葉盛茂16號發出聲明表示，他有向檢察總長陳聰明口頭報告前總統陳水扁的媳婦黃睿靚在海外開戶的相關情資。

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then 這個字用得很多，國中就知道是它是副詞，所以一開始讀到 then-president 雖然大致可以知道意思是「當時的總統」，不過還以為這個特別的 [名詞片語] 是 [副詞 + 名詞] 呢！其實，then 這時的用法是形容詞，then-president 就等於是 former president「前總統」的意思。

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more example

In the 1992 debates with Democrat Bill Clinton and
Independent candidate Ross Perot, then President George
H. W. Bush appeared bored with the discussion and at one
point was caught on camera looking at his watch.

1992 年，在與民主黨的 Bill Clinton 和無黨參選人 Ross Perot 的辯論時，前總統 George H. W. Bush 顯得對議題感到無聊，在他看錶的時候被攝影機抓到到鏡頭。