S: (n) doubt, dubiousness, doubtfulness, question (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"
Verb
S: (v) doubt (consider unlikely or have doubts about) "I doubt that she will accept his proposal of marriage"
S: (v) doubt (lack confidence in or have doubts about) "I doubt these reports"; "I suspect her true motives"; "she distrusts her stepmother"