1. (

• doubt ,
• uncertainty ,
• incertitude ,
• dubiety ,
• doubtfulness ,
• dubiousness

) the state of being unsure of something ;

2. (

• 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" ;