从雅思阅读考试的题型特性出发，可以归类为主旨题和细节题。其主旨题考核的是考生的总结归纳能力，细节题则相应考核定位查找能力。同时，这两类题型都考查对文字的理解，那么我们应该怎样看待“理解”二字呢?
在雅思阅读考试中，“理解”就是要能够正确识别用两种不同表达方式描述的同一事物。考查这种“理解”能力的唯一手段就是使用“同义替换”。本文对各种“同义替换”方式进行一一拆解，力求各位考生对“同义替换”这一考试工具了如指掌。
1词性之间的替换
词性的替换主要是指题目中的关键信息与原文中的内容在词性上做了变化而已。这样的替换相对来说，难度系数偏低，只需要考生能够辨认出相同的词根即可。
Example 1：
Cambridge8，Test3中Q35：Through mutations, organisms can 35 better to the environment.首先通过mutation一词将此填空题在原文定位到第C段”Because of changes in the genetic material (mutations) these have new characteristics and in the course of their individual lives they are tested for optimal or better adaptation to the environmental conditions.”然后寻找空后关键词better to，根据空格前的情态动词can推测空格处只能填一个动词，而且是原形，还要能和to搭配。这么一来，这句话里只有一个对应词比较合适：adaption，将其变形为动词adapt即可。
Example 2：
Cambridge6，Test2中Q17Q18：This is largely due to developments in 17 , but other factors such as improved 18 may also be playing a part.定位到原文第四段”Clearly, certain diseases are beating a retreat in the face of medical advances. But there may be other contributing factors. Improvements in childhood nutrition in the first quarter of the twentieth century….”表明有些疾病是被medical advances打败的。根据空格前的介词可以判断17题缺一个跟developments相关的名词。正确选项是medical的同根词M(medicine)。而18题是一个被improved修饰的名词，原文中improvements是它的同根词，所以答案是选项J (nutrition)。
这样的替换，即使单词是陌生的，却可以通过相同的词根或词形来帮助考生去挑选答案。要想掌握好这样的替换，也就要求考生尽可能地去多熟悉英语词汇中各种词根与词缀的应用。
剑桥阅读中出现的同根词变身：
ability → able
diabetic → diabetes
secrete → secretions
fertilise → fertilisers
creativity → creative
investigative → investigate
prefer → preference
emit → emission
predictability → predicted
2同义词/近义词之间的替换
同义词替换是指考题与原文中的关键内容用同义词进行一种互换。此类替换占据同义替换现象的大部分内容，而且几乎所有的题型都会有这样的替换现象。且大量常见的词都会主要是以名词与动词为主。
Example 3：
Cambridge6，Test4的Q9：Kim Schaefer’s marketing technique may be open to criticism on moral grounds.在原文第三段中定位到”Selling pharmaceuticals is a daily exercise in ethical judgment,”其中ethical即为原文中moral的同义词。
考生只需要在平时增加词汇量时有意识地去注意一些常见同义词，雅思阅读的解答也就变得简单很多了。其实严格意义上来讲，同义词应该还包括一些常用词组或短语之间的一种互换。
Example 4：
Cambridge7，Test4的Q19：Between 1940 and 1959, there was a sharp decrease in Alaska's salmon population.此题为是非判断题。利用between 1940 and 1959定位到原文第4段Between 1940 and 1959, overfishing led to crashes in salmon population so severe that in 1953 Alaska was declared a federal disaster area. 原文中的crashes与题干中的sharp decrease属于近义词(语义相同的词)之间的替换。
Example 5：
Cambridge6，Test1的Q38Q39：In recent years, many of them have been obliged to give up their 38 lifestyle, but they continue to depend mainly on 39 for their food and clothes.定位到原文D段：Over the past 40 years, most have abandoned their nomadic ways and settled in the territory’s 28 isolated communities, but they still rely heavily on nature to provide food and clothing.题干中提及被迫放弃什么生活方式，因此要求填一个形容词来修饰lifestyle。而时间状语in recent years是定位词。按顺序原则，原文的时间状语over the past 40 years正好跟in recent years对应，abandon与give up，ways和lifestyle对应，答案便是abandon后面的宾语ways的修饰语nomadic。同时判断depend on后面需要填一个名词，即依靠什么东西。而后面的food and clothes是非常好的定位词。很快可以在原文中找到对应depend on的rely on,而后面又有food and clothes。因此可以很清楚地判断出rely on的宾语nature就是答案。
剑桥中出现的同义词/近义词
change → shift / revision
overstate → exaggerate
target → goal
comments → feedback
performance → achievement
metropolitan → city
world → global
perceive → sense / feel
calculate → measure
resemble → look like
link to → associated with
expert → scientist
hard to find → elusive
3.否定加反义之间的替换
Example 6：
Cambridge7，Test1的Q33：In the follow-up class, the teaching activities are similar to those used in conventional classes.根据顺序原则以及follow-up可以定位到原文第6段。Such methods are not unusual in language teaching.题干中similar to和原文的not unusual属于否定加反义之间的替换。
Example 7：
Cambridge8，Test3的Q38：In principle, it is possible for a biological system to become older without ageing.可以定位到原文第三段Thus ageing and death should not be seen as inevitable, particularly as the organism possesses many mechanism for repair.题干中possible是原文not inevitable的否定加反义替换。
剑桥阅读中出现的否定加反义替换
downward → not rising
not traditional → radical new approaches
with no rain at all →droughts
4.上下义词之间的替换
所谓上下义，是指替换的词语之间通常有一种从属关系。在雅思的阅读中这类替换往往出现在段落配对题之中，题目中给的是一个具有属性或者是表示概念的词语，而在原文中出现的替换词却是一个具体或者是细节的信息，考察考生对这两者之间从属关系的配对。
Example 8：
Cambridge6，Test3的Q28：Studies show drugs available today can delay the process of growing old。此题为是非判断题，定位词为“drugs”，在原文中定位，我们能在文章第一段找到“As researchers on aging noted recently, no treatment on the market today has been proved to slow human aging—the build-up of molecular and cellular damage that increases vulnerability to infirmity as we get older”。原文中treatment即为题干中drugs的上义词。
Example 9：
Cambridge7，Test1的Q5：early military use of echolocation 。此段落信息配对题在原文定位的句子是“it was only a matter of time before weapons designers adapted it for the detection of submarines.之所以这样定位，就是原文中weapon一词作为题干中military的下义词出现。
剑桥阅读中出现的上下义词替换
chemical → fertilizer and pesticide
military → Second World War
body language → gesture
farming → grow plants and herd animals
environment → light, sound and warmth
四种难度依次递增的同意替换，使雅思阅读的考题显得变换无穷，同时也将阅读的难度提到了一个不同的高度。所以有很多考生抱怨，题目特点和解题技巧都很清楚，定位词也能找准，可就是定位不到题目在原文中对应内容的位置。其实这源于考生没有真正了解雅思阅读考查词汇的变形。所以考生只要掌握4、6级词汇，熟悉以上四种替换原则，在原文中寻找这些替换表达，即可快速且准确地完成定位和答题。
