doubt可以用作名词和动词，是一个常用及常考的词。下面谈谈doubt常见搭配及使用注意点。
1.名词doubt常见意思是“疑惑；疑问；不确定；不相信”。比如：There was little doubt in my mind.我心里几乎没有疑问。There seemed to be no doubt about it.此事似乎毫无疑问。There is little doubt that man has had an impact on the Earth's climate.毫无疑问人类对地球上的气候造成了影响。
doubt用在否定句或疑问句中时，它后面的从句应该是that从句。比如：
There is no doubt at all that we did the right thing. 毫无疑问我们做得对。There is no doubt about her suitability for the job.毫无疑问，她适合做这个工作。
Is there any doubt that he is guilty?肯定他有罪吗?
需要注意的是：There is no do doubt that …是一个常见句型，在使用这一句型时，不要错误地写成It is no doubt that…。这在考试的完型填空中也比较常见。
doubt用在肯定句中时，后面的从句多为whether引导的从句。比如：There is some doubt whether he is guilty.还不能确定他是否有罪。
2.doubt作为动词的意思是“无把握；不能肯定；怀疑，不相信”。比如：
There seems no reason to doubt her story. 似乎没有理由怀疑她所说的话。I had no reason to doubt him. 我没有理由不相信他。
如果动词doubt用在否定句或者疑问句中时，宾语从句用that引导。比如：
never doubted that she would come.我从未怀疑过她会来。Do you doubt that it is true?你怀疑她是真的吗？No one doubted his ability.没有人怀疑他的能力。
如果doubt用在肯定句中时，宾语从句用whether 或if引导，这也是在完形填空题中常常见到的。比如：I doubt whether/if the new one will be any better. 我不敢肯定这个新的是否会好些。I doubt whether/if it is true.我怀疑这是否是真的。I doubt whether/if such book would sell.我怀疑这样一本书是否有销路。
Many people doubted whether that would happen.很多人都怀疑那会不会发生。Students doubted if they would learn anything new from the young teacher.学生们怀疑他们是否能从年轻老师那里学到什么新东西。
