to not know

• 我事先不知。

  I didn't know beforehand.

• 不知自爱

  have no self-respect

• 不知者不罪。

  Sins of ignorance can be forgiven.

• 房间里黑洞洞的, 不知是大清早呢, 还是已经到了夜晚。

  The room was pitch black and it was impossible to tell night from day.