1. 怀疑;疑虑
    If you have doubt or doubts about something, you feel uncertain about it and do not know whether it is true or possible. If you say you have no doubt about it, you mean that you are certain it is true.

doubt是什么意思

    e.g. This raises doubts about the point of advertising...
           这对做广告的意义提出了疑问。
    e.g. I had my doubts when she started, but she's getting really good...
           她刚开始做时我心存疑虑，但她真的做得很好。

2. 不能肯定;认为…未必可能
    If you doubt whether something is true or possible, you believe that it is probably not true or possible.

doubt

    e.g. Others doubted whether that would happen...
           其他人认为那未必会发生。
    e.g. He doubted if he would learn anything new from Marie...
           他认为他不太可能从玛丽那儿学到任何新东西。

3. 怀疑（某事物的真实性）
    If you doubt something, you believe that it might not be true or genuine.

    e.g. No one doubted his ability...
           没有人怀疑他的能力。
    e.g. Nobody that I spoke to doubted his sincerity as a politician.
           和我谈过话的人中没有一个怀疑他作为一个政治家的诚意。

4. 怀疑，不相信（某人或某人的话）
    If you doubt someone or doubt their word, you think that they may not be telling the truth.

    e.g. No one directly involved with the case doubted him...
           与此案直接相关的人中没有人怀疑他。
    e.g. I still have no reason to doubt his word.
           我还是没有理由怀疑他的话。

5. 无疑地;确实地
    You say that something is beyond doubt or beyond reasonable doubt when you are certain that it is true and it cannot be contradicted or disproved.

    e.g. A referendum showed beyond doubt that voters wanted independence...
           全民公决无疑显示选民支持独立。
    e.g. His ability is beyond any doubt.
           他的能力毋庸置疑。

6. 不能肯定的;拿不准的
    If you are in doubt about something, you feel unsure or uncertain about it.

    e.g. He is in no doubt as to what is needed...
           他很确定需要什么。
    e.g. When in doubt, call the doctor.
           如有疑问，请联系医生。

7. 我怀疑;我认为不可能
    You say I doubt it as a response to a question or statement about something that you think is untrue or unlikely.

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    e.g. 'Somebody would have seen her.' — 'I doubt it, not on Monday.'
           “可能有人见过她。”——“我认为不可能，不可能在星期一。”

8. 可疑的;不确定的;不可靠的
    If you say that something is in doubt or open to doubt, you consider it to be uncertain or unreliable.

    e.g. The outcome was still in doubt...
           结果仍不确定。
    e.g. That claim is increasingly open to doubt.
           那一说法越来越可疑。

9. 无疑地;必定
    You use no doubt to emphasize that something seems certain or very likely to you.

    e.g. The contract for this will no doubt be widely advertised...
           关于这个的合约无疑会受到广泛宣传。
    e.g. She's a very sweet woman, as you no doubt know by now.
           她是一个非常温柔的女人，你现在肯定知道了。

10. 固然;诚然
    You use no doubt to indicate that you accept the truth of a particular point, but that you do not consider it is important or contradicts the rest of what you are saying.

    e.g. No doubt I'm biased, but it was the most cruel, evil human face I ever set eyes on...
           我固然是有偏见的，但那是我所见到的最残忍、最邪恶的人。
    e.g. No doubt many will regard these as harsh words, but regrettably they are true.
           固然会有很多人认为这些话过于刻薄，但是遗憾的是这些都是真话。

11. 无疑地;确实地
      If you say that something is true without doubt or without a doubt, you are emphasizing that it is definitely true.

doubt

      e.g. Without doubt this was the most important relationship I developed at college...
             这无疑是我在大学时期建立的最重要的关系了。
      e.g. The refugees, without a doubt, are the most vulnerable.
             难民无疑是最易受到伤害的。

12. the benefit of the doubt -> see benefit
      a shadow of a doubt -> see shadow