Basic Rules of Hanyu Pinyin – Set Phrases (chéngyǔ)
  1. Four-character Set Phrases that can be divided into two halves are linked by a hyphen. For example:
    • céngchū-bùqióng (happens/ed endlessly),层出不穷
    • guāngmíng-lěiluò (be righteous) 光明磊落
  2. All other four-character set phrases and well-known expressions (shúyǔ) that cannot be readily segmented are linked. For example:
    • bùyìlèhū (Isn’t it a happy thing?)不亦乐乎
    • àimònéngzhù (Sorry that I can’t help you).爱莫能助