n. uncertainty about the truth or factuality or existence of something; "the dubiousness of his claim"; "there is no question about the validity of the enterprise"

n. the state of being unsure of something

v. consider unlikely or have doubts about; "I doubt that she will accept his proposal of marriage"

v. lack confidence in or have doubts about; "I doubt these reports"; "I suspect her true motives"; "she distrusts her stepmother"

v. suspect to be false