一、which可以做疑问代词和关系代词。

1. 用作疑问代词时，意思是"哪一个,哪一些"

Which is my seat? 哪个座位是我的?

2. 用做关系代词时，意思是"那一个,那一些"

He also had a gun with which to . 他还有一把自卫用的枪。

二、That可以做副词，代词，形容词和连词，但是做连词时是最常见的，也是最难鉴别的，that 用作连词，引导名词性从句,状语从句和强调句。

1. that在名词性从句中。

①引导宾语从句。及物动词后的引导词that可省略。

I didn't (that) he could win the .

The out that Tom was not hard .

②引导主语从句。通常采用it作形式主语的句型。

That the earth goes the sun is known to .

(It is known to that the earth goes the sun.)

③引导表语从句。

The is that we are short of money.

④引导同位语从句。

引导同位语从句的that和引导定语从句的that是不同的。前者只起语法作用，在从句中不作任何成分;而后者在定语从句中作主语、宾语或表语。举例说明：

The news that he from us.

The idea that he holds is very on .

2. that引导状语从句

①引导目的状语从句。

Bring it that I may see it .

②引导结果状语从句。

What have I done that he be so angry with me?

③引导原因状语从句。

I am that I will fail in the test.

④引导让步状语从句。意为"虽然、尽管"。

that/as the task was, they to it on time.

⑤引导条件状语从句。意为"假使、假设"。

that you were in my , what would you do?

On that you were lost in the , you ask for help as soon as .

3. 引导强调句。

It is Mrs. White that makes the in her , not her meek .

It is an ill wind that blows good.

附加：that引导定语从句(做关系代词)

Is he the man that wants to see you?

The that you are is about to come .

三、where可以做副词，连词，和代词。

当副词时，可分为疑问代词和关系代词：

1. (用作疑问副词)在哪里往哪里从哪里在哪一点上

The asked me where I to go.

司机问我想去哪里。

Where shall we go?

我们去哪里?

2. (用作关系副词,引导关系从句)在那里往那里

That's where we .

那是我们的分歧所在。

This is the city where I was born.

这是我出生的城市。

当连词引导地点状语从句，意思是"在...处到...的地方...的地方"

I'll meet him where I first met you.

我将在初次见你的地方与他会面。

当代词，意思是"哪里,何处"

Where does he come from?

他是哪里人?

四、While可以做名词和连词，做连词时又可分为从属连词和并列连词。

做从属连词可以引导时间状语从句，让步状语从句，条件状语从句。

(1)引导时间状语

.趁热打铁。

(2)引起让步状语从句，意思是"虽然...但是...."、"尽管...但是..."(多放于句首)

nts，em..

虽然他爱他的学生，可是他对他们很严格。

(3)引起条件状语，意思是"只要"

.

只要生命存在，就有希望。

While作并列连词用，意思为"而，然而"，表对比。而but表转折。

，.

蜂蜜很甜，但蜜蜂有刺蜇人。