have (your) doubts about (doing) sth = feel unsure whether something is true or the right thing to do: ‘We have our doubts about sending Kevin to a boarding school.’ ‘Any doubts she’d had about marrying him soon disappeared.’ 3
I doubt that she is telling the truth.
I doubt whether she is telling the truth. When doubt is used to express certainty or near certainty, it is usually followed by a that-clause: There’s no doubt that he’s innocent.’ ‘I’ve no doubt that he’s innocent.’ ‘I’m in little doubt that he’s innocent.’ ‘I don’t doubt that he’s innocent.’ In this meaning, doubt is used with a negative word, e.g. not/no/little/not much. When doubt means ‘think that something is unlikely’, it is usually followed by if/whether: ‘I doubt whether he’s innocent.’ (= I think that he is probably guilty) ‘She doubts whether she’ll be able to come on Sunday.’ Note that some people may also say ‘I doubt that he’s innocent’, but careful users regard this as incorrect. 4
There is no doubt that she doesn’t want the job.
She obviously doesn’t want the job. There is no doubt that most parents are willing to spend a lot of money on their
child’s education .
Most parents are willing to spend a lot of money on their child’s education. There is no doubt that is usually used in formal styles when you want to persuade someone that what you are saying is true: There is no doubt that the present government has lost a great deal of support.’ This phrase is sometimes used when a ‘lighter’ expression (e.g.