在雅思写作中，一般的简单句会用一个形容词做定语来修饰一个名词，但当定语成分太过复杂而不能只用单个形容词担当时，就要借助于一个句子来做定语修饰名词。

像这样由句子担当定语，对被修饰的先行词进行有限定制约，使该词的含义更具体，更明确，我们称之为限定性定语从句，下面我们结合例句进行对比学习：

a)I don’t like lazy people(形容词做定语放在名词前面).

b)I don’t like the people who never keep their words. 我不喜欢从不遵守诺言的人.

在限定性定语从句中，有两个比较重要的概念。以b句为例，独立主句是：I don’t like the people；定语从句为“who never keep their words”，相当于一个形容词，做定语修饰名词“the people”， 且从句和主句是由who来连接的。在定语从句中，“the people”被称为先行词，指被定语从句所修饰或限制的对象。“who”被称为关系词即重复指代先行词，并在定语从句中充当一定成分的连词。

从上面的解析不难看出，关系词在限定性定语从句中很重要，是连接主句和从句的关键。关系词可以分为关系代词和关系副词，下面我们一起来进行具体的学习。

I.关系代词主要有：who， whom， whose， which， that.

A. 当先行词为人时，可用关系代词who，whom，whose 和that.

a. 若关系代词在从句中做主语时，选用 who 或that.

eg：The woman is a responsible teacher who /that is loved by her students.

= The woman is a responsible teacher and she is loved by her students.

b. 若关系代词在从句中做宾语时，选用 whom(首选)，who 或that.

eg： The girl whom we are talking about is a good friend of us.

c. 若关系代词在从句中做定语，表示人的所有关系时，选用 whose 或of whom.

Eg：I know a friend whose sister is a famous dancer.

= I know a friend. His sister is a famous dancer. (whose 代替了his，指人 friend)

B.当先行词为物时，可用关系代词which， that 或whose.

a. 若关系代词在从句中做主语或宾语时，选用 which 或that.

Eg：These are the trees which / that are destroyed in the fire(做主语).

b. 若关系代词在从句中做定语，表示物的所有关系时，选用 whose 或of which.

Eg：The children saw an elephant whose legs were hurt badly.

综上所述，当先行词为人和物时，若在从句中做主语或是宾语，这时可用选用关系代词that，做定语时用whose.

II. 关系副词主要有：where，when 和why.

A. 当先行词为表示地点的名词时，定语从句由副词where引导.

In the sixth century BC， ancient greece was a country where there were a lot of new ideas.

B. 当先行词为表示时间的名词时，定语从句由副词when引导.

Plato lived at a time when philosophy was very fashionable.

C. 当先行词为表示原因的名词时，定语从句由副词why引导.

Can you tell me the reason why you lied to me？

需要注意的是，限制性定语从句不能被省略，否则句意就不完整，例如I met someone who said he knows you.

通过上面的讲解，同学们在雅思写作过程中对限定性定语从句是否又多了一份了解呢？希望可以有助于您更好的解析英文中的定语从句，从而更好的提高雅思作文中的长难句学习。

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