关系词that在口语或书面语中的省略现象屡见不鲜。归纳起来，大致有以下几种：

1. 关系代词that在句中作主语时可以省略

(1) 当句子以who、what等疑问代词开头时that可以省略。如：

What is the stuff about the door (that) swings both ways?

在门上摇来晃去的是个什么东西？

Who was the man (that) called on you a moment ago?

刚才来拜访你的那个人是谁？

(2) 当关系代词that后面紧跟了ever，其前的先行词被first、only、last等词或形容词最高级修饰时that可以省略。如：

She was the first woman (that was) ever climbed Mt. Qomolangma.

她是登上珠穆朗玛峰的第一位妇女。

He is the bravest man (that) ever breathed.

他是空前的勇士。

It was the strangest sight (that was) ever seen.

这奇观是罕见的。

(3) 在I think、I feel、I know、he believes等插入语前作主语的关系代词that也可省略。如：

They’ve worked out a new plan (that) he believed is practical.

他们制订出了一个新计划，这个计划他认为是切实可行的。

He stopped his son from doing things (that) he thought were wrong.

他不让他的儿子干他认为是错误的事情。

(4) 在there、here、it、that等词开头的句子中关系代词that可以省略。如：

There was a man (that) came (who) said that he bought many different magazines.

有个人进来说过他买了各种杂志。

That’s thing (that) might happen to any man.

这种事谁也难免。

Here are the three of us (that) pass our time agreeably enough.

我们三个人在这儿过得真愉快。

(5) 如果先行词为两个或两个以上的that关系从句所修饰，则只须保留第一个作主语的关系代词，其后的均可省略。如：

Apart from repeating sentences that begins in the same way or (that) follow a similar structural pattern, you can repeat key words or phrases at various places within the paragraph.

除了以同样的方法或者以相同的句型结构重复句子以外，你还可以重复本段里各处的关键词语即单词或短语。

2. 关系代词that在句中作表语时可以省略

People said he was everything (that) an honest man should be.

人们说他具备了一个正直的人应有的一切美好品质。

He is not the impractical bookworm (that) he used to be.

他已不是以前那样不切实际死读书的人了。

3. 关系代词that作关系从句中动词的宾语时一般都可省略

The speech (that) he has made today is not a circumstance to his yesterday’s pronouncement.

他今天的讲演远不及他昨天发表的声明。

I’ll give you anything (that) you ask for.

你要什么我就给你什么。

4. 关系副词that作状语时完全可以省去

I liked the way (that) she organized the meeting.

我喜欢她组织这次会见的方式。

1949 was the year (that) the People’s Republic of China was founded.

一九四九年是中华人民共和国成立的年份。

5. 分裂句中的关系词that可以省略

It is you yourself (that) is hunted down. 

要追捕的就是你本人。

If it is I (that) you do love, how can it be that you look and speak so?

倘若你真正爱我的话，那么你怎么会用这种眼光看着我，这样对我说话呢？

It was Mr. Cooper (that) I gave the letter to.

我把那封信交给了库柏先生。

And I’m grateful to him. It’s because of him (that) I have the children, the horse, all those nice books about the eighteenth century.

我非常感激他，正是因为有了他，我才有了那些孩子，那匹马，所有那些有关十八世纪的好书。