for certain
肯定地, 确凿地, 无疑地
例句与用法：
I don't yet know for certain.
我知道得不确切。
I couldn't say for certain when he'll arrive.
我说不准他什麽时候到。
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。
I can't say for certain.
我说不准。
I don't know for certain.
我确实不知道。
I can't say for certain what to do.
我说不准该做什么。
I can't say for certain when he will arrive.
我说不准他什么时候会来。
肯定地
I don't know for certain.
我无法肯定。