“下定義”，【個人感覺其實下定義是論證方法的一種】可以給讀者一個直觀的概念或者清晰的思路，并且有利于后文的發展，而它本身并非只是字典上的解釋，可以靈活使用。接下來，將介紹一些它在大作文不同階段里的應用：

（一）引言段中的應用
1. Globalization
Globalization—the international spread of products, ideas and information—is bringing the world closer together. But globalization is not a new concept. For thousands of years，nations have roamed the earth in search of new markets and new sources of raw materials for their own industries.
關于“全球化”這個名詞，考生并不陌生，但是如何用合理的語言來賦予它一個含義，這并非易事，上述的引言段就很好地做到了這一點，先是從字面上詮釋了“全球化”的定義，進而又從實際生活角度賦予了它另外一層含義。

2. Telephone/Mobile phone
Imagine using smoking signals，carrier pigeons or riders on horseback to send an important message. Although those methods may sound strange，years ago people used them to communicate. Today，all a person has to do is pick up a telephone/mobile phone.【文章有新意，用對比的方法引出手機的定義，對比中又幽默含蓄的批判。我喜歡】
對于電話這一現代通訊工具，地球人都知道它是干嘛的，不過呢，我們可以從對于電話功能的定義上做文章，同樣也可以賦予它一個生動的含義，并且一下子可以吸引讀者眼球。

3. Studying abroad
Every year，students around the world leave behind the comforts of home to pursue a study-abroad experience in a foreign country. While many would say that studying abroad is advantageous，some would argue otherwise.【簡簡單單，切中肯綮，有的時候，平平淡淡才是真】
出國留學同樣是一個非常熟悉的話題，若直接用字典上的定義直接去解釋它顯然多此一舉，因此，我們不妨從側面突破，通過引入大量學生出國留學的事實和目的來詮釋這個再也不能熟悉的話題，同樣可以起到很不錯的效果。

4. Success
As Thomas Edison once said，“If you wish to succeed，you should use persistence as your good friend， experience as your reference，prudence as your brother and hope as your sentry. ”This essay is going to look at factors that constitute success.【在文章開頭寫名人名言，要三思而行，開頭寫名言的同學直接被“槍斃”的比比皆是】
“如果你希望成功，當以恒心為良友、以經驗為參謀、以謹慎為兄弟、以希望為哨兵。”這是偉大的美國發明家愛迪生曾經說過的一句話，借助名人名言來下定義又是一種非常有效的開頭方式，這樣做一方面揭示了文章接下來的主題，另一方面也增強了說服力，可謂是一舉兩得。

（二）主體段中的應用
1. Some people think that universities should provide graduates with the knowledge and skills needed in the workplace. Others think that the true function of a university should be to give access to knowledge for its own sake，regardless of whether the course is useful to an employer. What，in your opinion，should be the main function of a university? (劍七Test 4)
以下是此題目一篇范文的第2個主體段：

However, reaching the conclusion that other functions，such as giving access to knowledge for its own sake，are no longer important is biased. For hundreds of years，especially in the west，the undergraduate education is，indeed， a liberal education，which means the undergraduates learn a wide range of curriculums such as psychology， economics， politics that has no direct relations to jobs. The upsides of this is that it firstly enables students to become broad-minded and help them lay a solid theoretical foundation，then they will be able to choose the most appropriate field based on their own interests for further studies.
這個段落的論述的中心是以傳授知識本身為目的，作者使用了“通才教育”這個在西方非常流行的教育方式為佐證，在給出“通才教育”定義的本身，又用定語從句補充到了和題目第2個論點間的關系，從而進行了有力的對比，深化了段落中心。

2. Education
When people leave school，they wish they could breathe a sign of relief and leave learning behind. However，learning should last a lifetime. You exercise your body to stay strong，and you should exercise your mind to stay sharp. ……
在這個關于教育的話題中，作者在論述時用終身教育的好處來詮釋教育的長期性和必要性，從而為下文的擴展作了很好的鋪墊和過渡。【這個例子中的下定義的例子很“隱晦”】

3. School should teach children academic subjects which will be beneficial to their future careers. Therefore，other subjects such as music and sports are not important. To what extent do you agree or disagree with this opinion?(08年5月22日A類考題)
Academic subjects，such as reading and writing，play a vital role in the education system. Apart from activating creativity and imagination，it helps students lay a solid foundation of knowledge. Some might say that academic subject is to a student as a rifle is to a soldier，without which he is unable to fulfill his mission……【這句話還是非常非常精彩的。用了修辭比喻，句型也很好】

在這個主體段中，作者在開頭便舉出了一些學術課程的具體內容，從而給讀者一個概念，同時也展現了作者對題目的解讀能力。接下來我們再來看一個相似的用法：
4. Why have not alternative energies already replaced fossil fuels?
There are also problems with production stability. The amount of energy we need varies throughout the day，and conventional energy production，such as coal and oil，can be increased or decreased based on these variations. Alternatives like wind and solar power are limited because they can only produce electricity when it is sunny or the wind is blowing.

在這篇分析型大作文里，作者通過對化石燃料和可替代燃料的對比，突出了前者的優點，也揭示了后者的不足。通過將一個名詞范圍中的具體例子舉出，是下定義的另外一種詮釋。

綜上所述，下定義可用于議論文的開頭或者主體段里，但是它一般不適用于用在結尾段中。除了字典上的定義外，建議考生還可以從這個名詞或短語的功能、目的、包含的具體例子等方面賦予它含義，這些方式都屬于下定義。
【解析】下定義的確是廣泛引用在雅思高分寫作中的一種技巧。希望大家用心體會。