同样的意思写成两句话可能会觉得拖沓，那么定语从句可以使同样的意思用一句话表达出来了。
例如，Bad books contain evil thoughts. In them, there might be much description about violence, superstition, and sex.
→ Bad books, in which there might be much description about violence, superstition, and sex, contain evil thoughts.
第二，状语从句。
平时练习用五种状语从句，原因状语从句，让步状语从句，条件状语从句，时间状语从句和目的状语从句，雅思写作当中前类是频率最高的，大家一定好好掌握。
1. 原因状语从句：常由because, as, since和for引导
Eg: Nonetheless, I am still in favor of space travel, for its merits far outweigh demerits.
尽管如此，我还是赞成太空探险，因为它的好处远远大于坏处。
2. 让步状语从句：常由although, though, even though/ if, as long as和notwithstanding引导
Eg: Although this view is wildly held, this is little evidence that education can be obtained at any age and at any place.
尽管这一观点被广泛接受，很少有证据表明教育能够在任何地点、任何年龄进行。
3. 条件状语从句：常由if, on the condition that和providing that引导
Eg: If you want to achieve something or intend to fulfill one of your ambitions, you must work hard, make efforts and get prepared.
假如你要取得成就或要实现你的雄心壮志，你必须努力工作、艰苦奋斗、准备好条件。
第三， 宾语从句。
不必说，在描述各方观点是宾语从句是最常用到的。
Eg: Some people claim that government should be mainly responsible for the environmental pollution.
一些人认为政府应对环境污染负主要责任。
Eg: Many experts point out that, along with the development of modern society, it is an inevitable result and there is no way to avoid it.
许多专家指出这是现代社会发展必然的结果，无法避免。
第四， 同位语从句。
用名词性从句来解释前面一个名词。
Eg: It is an undeniable fact that environmental pollution becomes increasingly serious.
环境污染变得越来越严重是不可否认的事实。
Eg: No one can deny the basic fact that it is impossible for average workers to master those high-technology skills easily.
没有人能否认这一基本事实：对于一般工人来讲，轻松掌握这些技术是不可能的。
第五，主语从句。
Eg: What has caught our attention is /It is noticeable that the environment in both the rural and urban areas is deteriorating.
值得注意的是农村和城市的生态环境都在不断恶化。
Eg: It is universally acknowledged that environmental pollution becomes one of the most serious problems in China or even the world as a whole.
众所周知，环境污染问题是中国乃至世界面临的最为严重的问题之一。
第六，强调句: It is + 被强调的内容 + that 这与主语从句是有区别的。
Eg: It is cars and factories that release a great deal of gases, polluting the environment.
汽车和工厂排放大量的废气，使得环境被污染。
第七，倒装句。
Eg: Only if the government will take some appropriate measures, will this intractable problem be tackled.
只有政府采取适当的措施，这个棘手的问题才能被解决。
第八，被动语态。
当主语不明或者不愿突出主语的情况下使用。
Eg: Every means should be tried to protect the environment on which people live.
人们应竭尽全力来保护我们赖以生存的环境。
第九， 分词结构：包括现在分词和过去分词。
Eg: Tourism, which is a rising industry, has become the major source of economy, playing crucial role in many Asian countries.
旅游业是一个新兴的行业，它成为经济的主要, 在很多东南亚国家起着尤为重要的作用。
Eg: To be more specific, government should stage some relevant laws or regulations to severely punish the factory producing a great number of pollutants and the people littering or spitting deliberately.
具体来说，政府应该出台相关法律法规对制造大量污染物的工厂及故意乱扔垃圾随地吐痰的人进行严惩。
第十，插入语。
表强调，这是一个稍微难一点的语法点，大家酌情使用。
它通常由一个词、一个短语或一个句子构成,位置较为灵活,可置于句首、句中或句末,一般用逗号或破折号与句子隔开。
Eg: Computer, an indispensable part in our life, has brought us great conveniences.
电脑，我们生活中必不可少的一部分，给我们带来了极大的方便。
Eg: College students, lacking social experience, are easily cheated.
大学生，没有社会经验，容易上当受骗。
