doubt 
英 [daʊt]  美 [daʊt] 
n. 怀疑；疑问；疑惑

v. 对……无把握；怀疑；不信；拿不准；恐怕

例句：
There can be little doubt that he will offend again. 

几乎可以肯定他会再犯。

There is some doubt as to whether the letter was sent. 

那封信是否已经寄出去了，这一点还不太确定。

Local inhabitants haven't the slightest doubt as to who is the rightful owner. 

对于谁是合法所有人这个问题，当地居民已是确信无疑了。

We have serious doubts. 

我们深感疑惑。