grammar - What's the difference between saying 私は日本語を話しません vs 私は日本語が話しません?

私は日本語を話しません

私は日本語が話しません

I've seen both versions on the Internet. Maybe only one is the correct version? Maybe both?

Answer

日本語が話しません is ungrammatical. It sounds very unnatural. The following is the summary of what is OK and what is not:

• 私は日本語を話しません: OK


• 私は日本語は話しません: OK


• 私は日本語が話しません: Wrong!


• 私は日本語を話せません: OK


• 私は日本語は話せません: OK


• 私は日本語が話せません: OK

話す is a transitive verb (like English "speak"), so basically its object must be marked with を. But there are several exceptions you have to consider.

• Exception (1): When the object is decorated by the topic marker, をは turns into は (or は replaces を).
  
  


• Exception (2): When the verb is potential, the object can be marked with が, too. (話せる is the potential form of 話す)
  
  


• Exception (3): Using two は in one sentence is fine in a negative sentence. 私は日本語は話します is still grammatical, but the second は will have a strong contrastive meaning.