我确信自己是正确的。

I'd convinced myself (that) I was right.

《牛津词典》

我可以确信地说他们当中没有人过去或现在是种族主义者。

I can confidently say that none of them were or are racist.

《柯林斯英汉双解大词典》

我确信是这样。

I am sure it is.

youdao

I am certain we would know that George Washington was the commander of our forces in our battle.

我十分确信你们都知道,乔治·华盛顿是战时美国军队的指挥官

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I'm not really sure who said it but it's in a Lynda Barry novel called "Cruddy".

我并不确定是谁说的,不过确信这是在林达·巴里的小说《压花》里的话。

斯坦福公开课 - Twitter之父Jack.Dorsey演讲：好奇和灵感的力量课程节选

And that's very nice, because this allows me to be sure that my FOR loop is going to terminate.

因为这让我确信我的FOR循环是会终止的,因为只要集合是有限的。

麻省理工公开课 - 计算机科学及编程导论课程节选