Meaning : The state of being unsure of something.
Synonyms : doubtfulness, dubiety, dubiousness, incertitude, uncertainty
Meaning : Uncertainty about the truth or factuality or existence of something.
Example :
The dubiousness of his claim.
There is no question about the validity of the enterprise.
Synonyms : doubtfulness, dubiousness, question
Meaning : Consider unlikely or have doubts about.
Example :
I doubt that she will accept his proposal of marriage.
Meaning : Lack confidence in or have doubts about.
Example :
I doubt these reports.
I suspect her true motives.
She distrusts her stepmother.