for certain

副词 for certain:

1. definitely or positively (`sure' is sometimes used informally for `surely')
   同义词：surely, certainly, sure, for sure, sure enough, sure as shooting

1. I don't yet know for certain.
   我知道得不确切。
2. I couldn't say for certain when he'll arrive.
   我说不准他什麽时候到。
3. For certain reasons I will be unable to attend the meeting.
   因为某种原因，我不能出席这次会议。
4. I can't say for certain.
   我说不准。
5. I don't know for certain.
   我确实不知道。
6. I can't say for certain what to do.
   我说不准该做什么。
7. I can't say for certain when he will arrive.
   我说不准他什么时候会来。