一、Ludicrous侧重指荒唐可笑（常有幽默感）。例如：

It's a completely ludicrous idea. [这主意真是荒唐透顶。]

It was ludicrous, but he was not amused. [样子可笑极了，可是他一点也不觉得有趣。]

It was ludicrous to think that they would agree to those proposals. [认为他们会同意这些提议，那就太可笑了。]

二、Preposterous侧重指反常或荒谬的可笑(常有不合理性)。例如：

Her thought was preposterous. [她的想法是荒谬可笑的。]

It was preposterous; it was impossible. [这太荒唐了，真不可想像。]

He hopes that his preposterous reasons may be understood. [他希望自己荒谬的理由能被人理解。]

三、Ridiculous侧重指滑稽到令人发笑的程度(常有轻蔑的想法)。例如：

It was an absolutely ridiculous decision. [这是一个绝对滑稽可笑的决定。]

The deal seems so attractive it would be ridiculous to say no. [这笔交易看上去太诱人了，要是拒绝它简直是笑话。]

Don Quixote may look ridiculous, but to me he is a tragic character. [唐吉诃德看起来很可笑，但我认为他是个悲剧人物。]

由上可知，英语同义词ludicrous、preposterous和ridiculous的词义只是基本意义相同而内涵意义不同。正如著名外国语言文学家、翻译家、教育家戴镏龄先生指出的那样：“同义词只是在各种程度上的近义词，所谓同是相对的说法，即核心的意义相同，而又不能在别方面没有这样那样的区别。”