中古汉语里否定词前的“了”字

The study of liao 了 used together with negative words in middle Chinese

中古汉语里,否定词前的"了",功能并不完全相同,其间经历了一个副词进一步虚化的过程。此种"了"字的功能有两种,其主要功能是加强否定语气。"了"在此期多与否定词连用,就是由这种特定的功能决定的。

In middle times, the word liao is used along with negative words. It does not have only one meaning and function, liao of this kind had two functions, the main function being strengthening the negative mood, therefore liao is selective to the negative words used together with it.