That在英語(yǔ)中是一個(gè)使用頻率很高的詞。它可用作代詞、連詞、關(guān)系代詞等，有時(shí)可以省略。但在以下幾種情況下that不可省略，使用時(shí)尤其需注意。
一、that用作代詞，指上文提到的人或事物(單數(shù)名詞)，且需一個(gè)后置定語(yǔ)來修飾，此時(shí)that不可省
Their cotton output of1997 was double than that of1 987.
Mary’s handwriting is far better than that of Peter .
二、that用作連詞，在so...that,such。。。that,in order thar等引導(dǎo)的狀語(yǔ)從句中，that不可省。
They started so early that they might arrive in tim e.
It is such a heavy box that nobody can move it.
He worked hard in order that he might catch up with the others.
三、that用作連詞，引導(dǎo)主語(yǔ)從句時(shí)，當(dāng)它放在主句謂語(yǔ)動(dòng)詞之前時(shí)，that不可省。
That he came late made his teacher angry.
That she was chosen made us very happy.
如用it作形式主語(yǔ)，把從句置于謂語(yǔ)動(dòng)詞之后時(shí)，that可以省略。例如：
It is a pity(that) he has made such a mistake.
It is obvious(that) he is right.
四、that用作連詞，引導(dǎo)表語(yǔ)從句和同位語(yǔ)從句時(shí)，that不可省。
The news that our team has won the match is true.
My idea is that we should get more comrades to do t he work.
五、that用作連詞，引導(dǎo)賓語(yǔ)從句時(shí)，如主句的謂語(yǔ)動(dòng)詞是及物動(dòng)詞make,find,see等時(shí)，且后有賓語(yǔ)補(bǔ)足語(yǔ)時(shí)，that引導(dǎo)的從句可置于賓語(yǔ)補(bǔ)足語(yǔ)之后，用it作形式賓語(yǔ)，此時(shí)that不可省。
We find it necessary that he will succeed.
He made it clear that he was not interested in this subject.
六、that用作關(guān)系代詞，引導(dǎo)定語(yǔ)從句時(shí)，當(dāng)它作為從句的主語(yǔ)時(shí)，that不可省。
All that have to do is to practise every day.
That’s the same man that asked me for money yesterd ay.
但如that作從句的賓語(yǔ)時(shí)，that可省略。
The letter(that) I received was from my father.
七、在強(qiáng)調(diào)句型 It iswas...that結(jié)構(gòu)中，that不可省。
It is English that Professor Li teaches us.
It was in Shanghai that I saw the film.
一、that用作代詞，指上文提到的人或事物(單數(shù)名詞)，且需一個(gè)后置定語(yǔ)來修飾，此時(shí)that不可省
Their cotton output of1997 was double than that of1 987.
Mary’s handwriting is far better than that of Peter .
二、that用作連詞，在so...that,such。。。that,in order thar等引導(dǎo)的狀語(yǔ)從句中，that不可省。
They started so early that they might arrive in tim e.
It is such a heavy box that nobody can move it.
He worked hard in order that he might catch up with the others.
三、that用作連詞，引導(dǎo)主語(yǔ)從句時(shí)，當(dāng)它放在主句謂語(yǔ)動(dòng)詞之前時(shí)，that不可省。
That he came late made his teacher angry.
That she was chosen made us very happy.
如用it作形式主語(yǔ)，把從句置于謂語(yǔ)動(dòng)詞之后時(shí)，that可以省略。例如：
It is a pity(that) he has made such a mistake.
It is obvious(that) he is right.
四、that用作連詞，引導(dǎo)表語(yǔ)從句和同位語(yǔ)從句時(shí)，that不可省。
The news that our team has won the match is true.
My idea is that we should get more comrades to do t he work.
五、that用作連詞，引導(dǎo)賓語(yǔ)從句時(shí)，如主句的謂語(yǔ)動(dòng)詞是及物動(dòng)詞make,find,see等時(shí)，且后有賓語(yǔ)補(bǔ)足語(yǔ)時(shí)，that引導(dǎo)的從句可置于賓語(yǔ)補(bǔ)足語(yǔ)之后，用it作形式賓語(yǔ)，此時(shí)that不可省。
We find it necessary that he will succeed.
He made it clear that he was not interested in this subject.
六、that用作關(guān)系代詞，引導(dǎo)定語(yǔ)從句時(shí)，當(dāng)它作為從句的主語(yǔ)時(shí)，that不可省。
All that have to do is to practise every day.
That’s the same man that asked me for money yesterd ay.
但如that作從句的賓語(yǔ)時(shí)，that可省略。
The letter(that) I received was from my father.
七、在強(qiáng)調(diào)句型 It iswas...that結(jié)構(gòu)中，that不可省。
It is English that Professor Li teaches us.
It was in Shanghai that I saw the film.