英文信函可分为正式和非正式信件两大类：

    ◆正式信件一般适用于写给陌生人（如托人办事、投诉咨询等）、职场人士（同事、老板、客户等）或者是写给院校机构的工作人员（比如你的导师）等等，总之写正式信件的时候，一定是正经的严肃的认真的！需要你斟词酌句，否则哪句话表达不恰当，分分钟可能面临人生危机！

    ◆非正式信件当然就是写给朋友啦、父母啦，一起聊聊八卦吐个槽神马的，更加随意，不拘小节。

    下面是一封投诉类正式信函（部分内容）和一封雅思G类小作文非正式信函（部分内容）的对照，细心的你发现什么区别了么？

    Formal 正式信件：

    Dear Sir or Madam,

    I am writing with regard to a flight that I missed due to a mistake by one of your employees........

    As a result of the error, I was not allowed to board the ight to Rome, and this caused me great inconvenience............

    As the mistake was caused by your company, I hope that you will compensate me for the cost of the additional flight, as well as for my taxi fares to and from the airport.

    I look forward to receiving your response.

    Yours faithfully,

    Paul Jones 

    Informal 非正式信件：

    Dear John and Jane,

   I hope this letter finds you well. I042m just writing to thank you both for the holiday and for the photos you sent.

   ........ You really were fantastic hosts, and I couldn042t have asked for better guides to show me around.

    Sorry I didn042t write to you earlier, but I042ve been working flat outsince the moment I arrived home. Do you remember I told you I had an assignment to finish? Well, the deadline was two weeks earlier than I thought it was!

   ..........

    Hope to see you soon,

   Peter

    从以上信件标注的内容来看，正式信函和非正式信函在表达上明显不同，好了，大家一起来找茬吧！