【Uncertainty】 , 【doubt】 ,  【dubiety】 ,  【dubiosity】 ,  【skepticism】 ,  【suspicion】 ,  【mistrust】  can all mean a feeling of unsureness about someone or something.

【Uncertainty】 stresses the lack of certainty or certitude that may range from a mere falling short of these to an almost complete lack of knowledge or conviction especially about the result or outcome of something.

【Doubt】 implies both an 【uncertainty】 about the truth or reality or status of something and an inability to make a decision, often even after study or investigation; frequently the term implies such a feeling or state of mind in respect to religious beliefs or doctrines.

【Dubiety】  (compare dubious under DOUBTFUL ) comes closer to  【uncertainty】  than to  【doubt】  , for it stresses a lack of sureness rather than an inability to reach a decision as to where the truth lies. But it regularly carries, as  【uncertainty】 does not, a strong implication of wavering or of fluctuations between one conclusion and another.

【Dubiosity】  is not always distinguishable from  【dubiety】 . Sometimes, however, it suggests not 【uncertainty】 , but vagueness, indistinctness, or mental confusion.

【Skepticism】 suggests in this, its general sense, an unwillingness to believe without demonstration or an incredulity while any plausible evidence to the contrary exists; it usually refers to a habitual or temperamental state of mind or to a customary reaction to something proposed for belief.

【Suspicion】  stresses conjecture or apprehension that someone or something is not true, real, or right or that he or it has worked or is working evil or injury, but it also implies that the conjecture or apprehension is accompanied by 【uncertainty】 or 【doubt】 , often to the extent that the term comes close to  【doubt】 .

【Mistrust】  (see also DISTRUST ) implies 【doubt】 that is based upon 【suspicion】 and that therefore precludes the possibility of one's having faith or confidence or trust in a person or thing.