doubt-n; 2 Senses

Sense Number 1: a belief state of uncertainty about something

Commentary: DOUBT[+state][+belief][+uncertainty]
NOTE: refers to an individual's internal belief state

I have my doubts that John will actually show up at the party.
He was filled with doubts about his own ability to lead the company.
Is it a wise thing to never doubt yourself?
His speech did a lot to alleviate the doubts in many voters' minds.

PropBank: doubt.01
WordNet 3.0 Sense Numbers: 1

Sense Number 2: an approximate measure of uncertainty

Commentary: DOUBT[+quantity][+measure][+approximate][+uncertainty]
NOTE: refers to a general, publicly available measure of uncertainty, not an individual's internal belief state (Sense 1)

The accuracy of this study has been cast into serious doubt.
There is no doubt that taxes will go up if their candidate is elected.
The prosecution has proven the defendant's guilt beyond any reasonable doubt.

PropBank: NM
WordNet 3.0 Sense Numbers: 2