thiếu chính xác không chắc chắn 
uncertain like: không chắc → →
Hier bin ich nicht sicher, ob deine Übersetzung korrekt ist. ☊ 
Tôi không chắc phần dịch này của anh / chị là chính xác. ☊ (Lektion 99, Nr. 1613) It appears unlikely that interest rates will fall further. ☊ appear ☊
certain (that)...: She wasn't certain (that) he had seen her. ☊ certain ☊
I'm not sure—I can find out for definite if you like. ☊ definite ☊
I'm not sure I can walk so far. ☊ far ☊
He's never done this type of work before; I'm not sure how he'll fit in with the other people. ☊ fit in (with sb/sth) ☊
Her future is uncertain. ☊ future ☊
I wasn't sure if I could handle such a powerful car. ☊ handle ☊
+ speech: 'I'm not sure,' she hesitated. ☊ hesitate ☊
She went through an identity crisis in her teens (= was not sure of who she was or of her place in society). ☊ identity ☊
'I'm not sure that's a good way to do it.' 'Let me be the judge of that.' ☊ judge ☊
'She's the worst player in the team.' 'Oh, I don't know (= I am not sure that I agree) —she played well yesterday.' ☊ know ☊
I still have mixed feelings about going to Brazil (= I am not sure what to think). ☊ mixed ☊
The future by its very nature is uncertain. ☊ nature ☊
One should never criticize if one is not sure of one's facts. ☊ one ☊
a period of consultation/mourning/uncertainty ☊ period ☊
The company's financial position is not certain. ☊ position ☊
We're not sure whether we still want to proceed with the sale. ☊ proceed ☊
I'm not sure if Karen is ready for marriage yet. ☊ ready ☊
relationship between A and B: I'm not sure of the exact relationship between them—I think they're cousins. ☊ relationship ☊
+ speech: 'I'm not sure,' she responded. ☊ respond ☊
She's a professor of something or other (= I'm not sure what) at Leeds. ☊ something ☊
For dessert there's a fruit pie of some sort (= you are not sure what kind). ☊ sort ☊
They had been invited to a Hindu wedding and were not sure what happened on such occasions. ☊ such ☊
'Is that John over there?' 'I'm not sure '. ☊ sure ☊
You don't sound very sure. ☊ sure ☊
sure how, whether, etc...: Ask me if you're not sure how to do it. ☊ sure ☊
I'm not sure whether I should tell you this. ☊ sure ☊
I think this is their house, but I'm not sure. ☊ think ☊
think sb/sth + adj.: I think it highly unlikely that I'll get the job. ☊ think ☊
I'm not too sure if this is right. ☊ too ☊
They're both uncertain about what to do. ☊ uncertain ☊
I'm still uncertain of my feelings for him. ☊ uncertain ☊
Our future looks uncertain. ☊ uncertain ☊
I'm not sure that I understand. Go over it again. ☊ understand ☊
unlikely (that...): It's most (= very) unlikely that she'll arrive before seven. ☊ unlikely ☊
I'm not sure that this is the most valuable use of my time. ☊ use ☊
'Do you want to come?' 'Well, I'm not sure.' ☊ well ☊
wish sb/sth to do sth: He was not sure whether he wished her to stay or go. ☊ wish ☊