a feeling of not being certain about something
doubt about/as to: There seems to be some doubt as to whether this is legal.
have no/little doubt that: I have no doubt that he will succeed.
there is little/no doubt that: There’s little doubt that the measures will be extremely unpopular.
raise doubts (=make you have doubts): The accident raised doubts about (=makes people have doubts about) the safety of the aircraft.
nagging/lingering doubts: Nagging doubts about her story do remain.
grave/serious doubts: I have serious doubts about whether this system will work.
Synonyms and related words