在雅思阅读考试中，同义替换是雅思阅读必不可少的考查方式，派生词替换、同义词或同义词词组以及反义词的否定形式是大多数学员比较熟悉的，但上义词替换下义词却是很多同学不太知道的，甚至从未听说过，在这里说一下对于上下义词的理解，和实战雅思阅读考试做题中的运用。

　　首先，我们先来明确上下义词的概念。范围大的词汇为上义词，而其下属的具体例子为其下义词。比如说，颜色colour和红色red就是一对明显的上义词和下义词。

　　上义词与下义词的概念弄明白后，咱们还要熟悉雅思阅读考查这类替换的方式，简而言之，就是“题上文下”——也就是说上义词会出现在题干中替换原文中的下义词。

　　其实，原因很简单，雅思阅读的命题人是根据原文中的具体信息来命题的，用范围较大的上义词colour来替换原文中更为具体的red就顺理成章了，下面咱们就通过多组题目来见识一下上义词与下义词在雅思阅读各种题型中的应用。

　　首先，我们来看一道判断题，选自C5-P42-Q13 Bakelite was only available in a limited range of colours。本题定位原文最后一段难度不大，但很多同学把最后一段看了一遍又一遍还是没有结果，大家也不妨试一下。

　　原文如下:

　　Baekeland's invention, although treated with disdain in its early years, went on to enjoy an unparalleled popularity which lasted throughout the first half of the twentieth century. It became the wonder product of the new world of industrial expansion - 'the material of a thousand uses,. Being both non-porous and heat-resistant, Bakelite kitchen goods were promoted as being germ-free and sterilisable. Electrical manufacturers seized on its insulating properties, and consumers everywhere relished its dazzling array of shades, delighted that they were now, at last, no longer restricted to the wood tones and drab browns of the pre-plastic era. It then fell from favour again during the 1950s, and was despised and destroyed in vast quantities. Recently, however, it has been experiencing something of a renaissance, with renewed demand for original Bakelite objects in the collectors' marketplace, and museums, societies and dedicated individuals once again appreciating the style and originality of this innovative material.

　　实际上，此题就运用了上义词替换下义词这一伎俩。我们可以通过colours 定位到原文这样的信息“no longer restricted to the wood tones and drab browns of the pre-plastic era”，也就是将colours替换了文中大部分学员比较熟悉browns。

　　由于看出limit与restrict的替换难度并不大，那么此题与原文中no longer矛盾，选FALSE也就很轻松了。

　　其实，不仅仅是判断题，在填空题中的应用也让不少学员尝到很多苦头。我们再看一个例子，选自C6-P29-Q40 ...........produce is particularly expensive，此题在原文中的定位难度也不大，很多学员都定位了如下的原文内容。

　　Provisions available in local shops have to be flown into Nunavut on one of the most costly air networks in the world, or brought by supply ship during the few ice-free weeks of summer. It would cost a family around ?7,000 a year to replace meat they obtained themselves through hunting with imported meat.

　　但是，具体答案定位哪一句，很多同学犯了难，原文中根本就没有与答案最为密切的produce。我们再仔细分析一下，原来题干中的produce（农产品）可以替换原文中meat，答案也就是imported了。

　　其实，相比以上两种题型，上义词与下义词在段落信息配对题的出现频率更高。

　　比如，C9-P93-Q18：

　　reference to a possible link between culture and a particular form of behaviour, 其中“a particular form of behaviour”替换了原文H段的“a struggle over toy”, 再比如C9-P43-Q5：a list of medical conditions which place some children more at risk from noise than others，其中“medical conditions”替换了原文D段的“hearing impairment, autistic spectrum disorders (ASD) and attention deficit disorders (ADD/ADHD)”。

　　我们发现，题干中的名词可能会作为上义词来考查，回原文定位时需要留意该词的具体化概念，并谨记“题上文下”的替换原则，多加联系，相信会有所提高。