情感和态度表达—— 肯定　Certainty

确定

I'm sure that this is Peter's car.我确定这是彼得的车。

There's no doubt that John would leave the company.无疑约翰要离开公司了。

不确定

We haven't decided yet.我们还没有做决定。

I'm not sure whether I want to accept that job.我还不确定是否要接受那份工作。