无疑的英文：
no doubt
undoubtedly

参考例句：

To lay bare without suspicion
坦然无疑

Of course
当然,自然,无疑

I can easily believe it .
我无疑能相信它。

Isn't that absurd? He's bound later on to run after women like the very devil.
你道好笑不好笑?将来色鬼无疑了!

The CPPCC will undoubtedly continue to perform a very useful role in this work.
政协在这一工作中无疑将继续发挥重要作用。

It is the undoubted right of the people of England to call them to account for it.
英格兰人民无疑有权要求他们对此作出解释。

There's no doubt Mr Putin's speech caught the mood of most deputies.
无疑，普金先生的讲话充分反映了大多数代表的心情。

This is doubtless due to the displacement of hand labour by machinery.
无疑这是使用机器代替手工所产生的结果。

The most influential of the modem type was undoubtedly the U. S. weekly Life (1936-72).
当代最有影响的无疑当数美国《生活>周刊(1936～1972)。

There are a number of devotees that will still certainly favor Starbucks over 'Brand X'.
无疑将有许多(咖啡)爱好者依旧偏爱星巴克,而不是别的品牌。

doubt是什么意思：
n. 怀疑；疑问；疑惑
v. 对…无把握；怀疑；不信；拿不准；恐怕

benefit of the doubt
裁判员对可疑情况无把握时不对有关运动员作不利判定

They were beset by doubts and fears .
他们被疑虑和恐惧所困扰。

Being such as to debar questioning or doubts.
无异议的如此以至使质疑或怀疑都没有必要的。

They have never doubted of success.
他们对成功从未怀疑过。

Doubt is the key of knowledge
怀疑乃知识的钥匙

undoubtedly是什么意思：
adv. 确实地，无庸置疑地

They have undoubtedly accomplished the task as planned.
他们无疑按计划完成了任务。

Kite is undoubtedly a class player.
凯特绝对是个一流选手。

This season is undoubtedly the best for this pitcher.
这个球季毋庸置疑是这个投手表现最好的一个球季。

The words undoubtedly give the air of positiveness.
毫无疑问，这些话增添了肯定的气氛。

The dissident elements are undoubtedly opposed to the King and in favour of republic
这些叛乱分子无疑是反对国王，赞成共和政体的。