He was uncertain about his brother's intentions. [+ about]

他拿不准他哥哥的意图是什么。

They were uncertain of the total value of the transaction. [+ of]

他们还不确定这笔交易的总价值是多少。

He stopped, uncertain how to put the question tactfully.

他停顿下来，犹豫着该如何巧妙地提出那个问题。

With some hesitation and an uncertain smile, she held out her hand.

她犹豫了一下，带着迟疑的微笑把手伸了出去。

How far the republics can give practical help, however, is uncertain.

然而，这些共和国究竟能够提供多少切实可行的帮助还未可知。

It's uncertain whether they will accept the plan.

还不确定他们是否会接受这一方案。

Students all over the country are facing an uncertain future.

全国各地学生前途未卜。

She told him in no uncertain terms to go away.

她明白无误地叫他离她远远的。