considerable, grave, real, serious, severe | slight
Without the slightest doubt this is a remarkable exhibition.

gnawing, lingering, nagging, niggling | growing, increasing | personal, private
He made clear his own private doubts about it.

reasonable
We have established beyond all reasonable doubt that the painting was indeed by Rembrandt.

religious

arouse, raise
His failure to appear raises serious doubts as to his reliability.

entertain, feel, harbour, have
She still felt the same niggling doubt: was he really telling the truth?

express, voice | clear up, dispel, remove, resolve
The announcement dispelled any doubts as to the prince''s intentions.

cast, throw
Her record of dismissals casts doubt on her ability to hold down a job.

call sth into, throw sth into
The proposed development has been thrown into doubt by the decision.

be open to
Their honesty is open to doubt.

appear, arise
Doubts have arisen over the viability of the schedule.

exist
Considerable doubt exists as to the precise origin of this custom.

persist, remain | surround sth
From the start, doubts surrounded her claim to be the missing heiress.

beyond (a/all/any) ~
The evidence proves beyond doubt that he is innocent.

in ~
The arrangements for the event still seemed to be in doubt. | If in doubt, consult your doctor.

without (a) ~
She is without a doubt the best tennis player I know.

~ about/over
Some committee members still harboured doubts about the plans.

beyond/without a shadow of (a) doubt
This proves without a shadow of doubt that we were right.

have your doubts about sth
They say they''ll be here on time, but I have my doubts about that.

seriously, very much
I never seriously doubted his story.

privately
Lee privately doubted the truth of this statement.