These are word's grammars related to doubt. Click on any word to go to its word's detail page. Or, go to the definition of doubt.
We can use no doubt when we think that what we are saying is likely to happen, or when we think it is true. It is similar to ‘I suppose’ or ‘I imagine’:
1 I doubt if, I don’t know whether
We use if or whether to introduce clauses after verbs of doubting: