雅思写作“下定义”在议论文中的用途

“下定义”，【个人感觉其实下定义是论证方法的一种】可以给读者一个直观的概念或者清晰的思路，并且有利于后文的发展，而它本身并非只是字典上的解释，可以灵活使用。接下来，将介绍一些它在大作文不同阶段里的应用：
（一）引言段中的应用
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.
关于“全球化”这个名词，考生并不陌生，但是怎样用合理的语言来赋予它一个含义，这并非易事，上述的引言段就很好地做到了这一点，先是从字面上诠释了“全球化”的定义，进而又从实际生活角度赋予了它另外一层含义。
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，用对比的方法引出手机的定义，对比中又幽默含蓄的批判。我喜欢】
对于电话这一现代通讯工具，地球人都知道它是干嘛的，不过呢，我们可以从对于电话功能的定义上做文章，同样也可以赋予它一个生动的含义，并且一下子可以吸引读者眼球。
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.【简简单单，切中肯綮，有的时候，平平淡淡才是真】
出国留学同样是一个非常熟悉的话题，若直接用字典上的定义直接去解释它显然多此一举，因此，我们不妨从侧面突破，通过引入大量学生出国留学的事实和目的来诠释这个再也不能熟悉的话题，同样可以起到很不错的效果。
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.【在文章开头写名人名言，要三思而行，开头写名言的同学直接被“枪毙”的比比皆是】
“如果你希望成功，当以恒心为良友、以经验为参谋、以谨慎为兄弟、以希望为哨兵。”这是伟大的美国发明家爱迪生曾经说过的一句话，借助名人名言来下定义又是一种非常有效的开头方式，这样做一方面揭示了文章接下来的主题，另一方面也增强了说服力，可谓是一举两得。
（二）主体段中的应用
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? (剑七Test 4)
以下是此题目一篇范文的第2个主体段：
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.
这个段落的论述的中心是大学以传授知识本身为目的，作者使用了“通才教育”这个在西方国家非常流行的教育方式为佐证，在给出“通才教育”定义的本身，又用定语从句补充到了和题目第2个论点间的关系，从而进行了有力的对比，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. ……
在这个关于教育的话题中，作者在论述时用终身教育的好处来诠释教育的长期性和必要性，从而为下文的扩展作了很好的铺垫和过渡。【这个例子中的下定义的例子很“隐晦”】
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类考题)
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……【这句话还是非常非常精彩的。用了修辞比喻，句型也很好】
在这个主体段中，作者在开头便举出了一些学术课程的具体内容，从而给读者一个概念，同时也展现了作者对题目的解读能力。接下来我们再来看一个相似的用法：
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.
在这篇分析型大作文里，作者通过对化石燃料和可替代燃料的对比，突出了前者的优点，也揭示了后者的不足。通过将一个名词范围中的具体例子举出，是下定义的另外一种诠释。
综上所述，下定义可用于议论文的开头或者主体段里，但是它一般不适用于用在结尾段中。除了字典上的定义外，建议考生还可以从这个名词或短语的功能、目的、包含的具体例子等方面赋予它含义，这些方式都属于下定义。