know for sure 明确知道

　　这是在表不很明确地知道某事时用到的表达。可以单独使用为 know for sure,也可以使用 know for sure 主语+动词的形态。没有自信时，经常会用作否定形式。

　　例句：

　　All we know for sure is that he seems to hate Liz as much as I do.

　　我们都知道，他像我恨莉斯一样恨她。

　　I think she might be a lesbian but I don't know for sure.

　　我觉得她是个同性恋，不过不太肯定。

　　She only suspects something. She doesn't know for sure.

　　她只是在怀疑断么，不过她也不太确定。

　　对话：

　　A: I know for sure I'll become a lawyer.

　　我敢肯定我能成为一个律师。

　　B: You'll have to study really hard.

　　你得努力学习了。