100% 确定

Absolutely
绝对地

【例句一】
Are you absolutely sure Jane said she wanted to quit?
你绝对肯定Jane说了她想辞职吗？

【例句二】
I'm absolutely sure I'll have this report finished by Friday. You can count on me.
我绝对肯定周五能把这个报告完成。你可以相信我。

Definitely
肯定地

【例句】
Mark says he's definitely sure he saw Kim and Marta at the bar last night.
Mark说他昨晚在酒吧肯定看到Kim和Marta了。

Entirely
完全地，彻底地

【例句】
How can you be entirely sure nothing will go wrong?
你怎么能完全肯定不会出差错？

80-90% 确定

Quite
很

【例句一】
I'm quite sure they'll approve our funding for the research.
我很确定他们会通过我们的研究经费。

【例句二】
Look at the sky. I'm quite sure it's gonna rain so we better get out of here.
看看天吧，我很确定要下雨了，我们赶紧走吧。

70-80% 确定

Pretty
挺，比较

【例句】
Pretty sure isn't good enough. I need you to be absolutely sure you want to do this.
挺确定不行，我需要你绝对的肯定能做好这件事。

Fairly
挺，比较

【例句一】
Nick's fairly sure the restaurant's on 5th Avenue, but we should check online.
Nick挺确定这个餐厅就在第五大道上，但是我们还是可以在网上查一下。

【例句二】
I'm fairly sure they'll agree to our terms.
我挺确定他们会答应我们的条件的。

50-60% 确定

Somewhat
差不多

【例句】
I didn't really talk with Fred about the situation, but I'm somewhat sure he's on our side.
我没真的跟Fred谈过这个情况，但是我差不多确定他站在我们这一边。

Not entirely sure
不是100%确定

【例句】
A: How sure are you?
你有多确定啊？
B: Well I'm not entirely sure. I'll have to do some more research.
哦，我也不是100%确定，我得做些调查。

Not sure
不确定

【例句一】
I'm not sure how much I paid for this computer. It was a long time ago.
我不确定当时买这电脑花了多少钱。很久以前的事了。

【例句二】
We're not sure where we're going for vacation. We haven't thought about it.
我们不确定要去哪度假。我们还没想过呢。