that
1.注意下面每组里的第一句里用that，第二句里用this：
- I shall go tomorrow- that is the only thing he said.
This is the only thing he said:'I shall go tomorrow. - How to avoid the trouble, that is the question.
This is the question: how to avoid the trouble.
每组第一句里的that改作this也可以，但第二句里的This决不可改作That。
2.可以说The study of idiom is as important as that of grammar，但不可说This is a point of idiom rather than that of grammar，该把that删去或改作one。第一句里的that代表the study。第二句里的that代表a point，但照习惯that只可代表the ...，不可代表a ...，所以第二句不对。下面第一组里的两句不错，第二组里的两句不对：
- The cost of wheat is less than that of rice.(that= the cost)
I prefer the climate of Shanghai to that of Tianjin.(that= theclimate) - A cake made of wheat costs less than that made of rice.(该把 that改作 one)
I prefer a street in a small town to that in such a large city as、Shanghai.(该把 that 改作 one)
3.注意and that在下面三句里的习惯用法：
- She came at midnight, and that alone. (and that＝and she came at midnight)
- He studied music for many years, and that under a well-known musician. (and that＝and he studied music for many years)
- The boy has lost a book, and that the one he bought only the other day. (and that＝and he has lost)
各句里的and that都加重后面的语气。
4.that happy three weeks（那快乐的三星期长的一段时间），that five years（那五年长的一段时间）等表达方式里可以用that，因为把three weeks，five years等当作一段时期（如three weeks指“三星期长的一段时间”，并不指“三个分开的星期”）。但不用that而用those也很普通。参见this 1
5.下面三种表达方式都可以说，意思相仿：
- the man mentioned
- the man who is mentioned
- that man who is mentioned
第三种表达方式语气最重。that man mentioned也有人用，但不算正当，下面各种表达方式也不算正当：
- that person named
- that boy following us
- that book at the top of the list
- that theory now in question
参见those 4
但有下面两点该注意：
（1）上面我所说不算正当的各种表达方式里的that是形容词，不是代词。that mentioned，that at the top of the list等表达方式里的that是代词，不是形容词，各种表达方式都可以说。
（2）that book known as the Bible，that little girl with brown hair等表达方式里的that是形容词，但因为它含有“就是你所知道的那个”的意思，所以不算不正当。
6.下面两句里的第一个that现在远不及从前普通，该改作such a或so great a：
He was wounded to that degree that he was rushed to hospital.
She has that patience that she never complains.
7.so... that和so... as不可混用，such... that和such ... as也不可混用，参见as 11
8.下面各句都是强势式，但两组的结构不同，参见it 5，6和7
- It is there that accidents often occur.
It is through carelessness that accidents often occur.
It is when the lights have gone out that accidents often occur. - It is help that I need.
It is I that need help.
9.that用作关系代词有下面几点该注意：
（1）现在可以说只用在限定从句里，不用在非限定从句里，如This is the pen that I bought yesterday里用that，但I have bought a pen, which I shall show you when you call里用which。下面两句里的that都不自然，最好改作which：
- We were looking at the moon, that was rising slowly.
- They are having a good time together in the park, that is now far less crowded than an hour ago.
注意下面每组里的两句意思不同，每组的第一句里没有逗号，第二句里有逗号：
- They have three houses hat(或which)are built of stone.(他们有三所用石头造成的房子[也许还有用其他材料造成的房子]。)
They have three houses, which(不用 that)are built of stone.(他们有三所房子,都是用石头造成的。) - The members that(或who)were present numbered fifty-one.(出席的会员共有51个[有些会员们不曾出席]。)
The members,who(不用that)were present, numbered fifty-one.(会员们都出席,共有51个。)
（2）that的前面不可用介词，如不可说This is the joke at that they laughed，该改作下面的任何一句：
- This is the joke at which they laughed.
- This is the joke that they laughed at.
- This is the joke which they laughed at.
- This is the joke they laughed at.
第一句最正式，最不普通，第四句最不正式。
（3）that that ...（…的东西）远不及that which普通。但注意下面两句里的that that...里的第二个that的先行项不是第一个that而是It。参见8
- It is that that I need。
- It is only that that keeps him busy.
（4）those who ...（…的人们）里用who比用that普通得多。all who...（…的一切人）里的who不可改作that。all that...是“…的一切东西”，不是“…的一切人”。he who...现在不及one who...普通，he that ...更不普通。下面各句都是谚语，不该摹仿它们：
- He that promises too much means nothing.
- He that respects not is not respected.
- He lives long that lives well.
- He cannot speak well that cannot hold his tongue.
- He who commences many things finishes but few.
- He who does not rise early never does a good day's work.
（5）8里所举的It is help that I need和It is I that need help两句里都用that，第一句里的that可以改作which，第二句里的that可以改作who，但都不及用that普通。
（6）在属于最高级的词的后面用that比用which普通。例如：This is the best specimen that we have got.
（7）在only后面用that比用which普通。例如：This is the only specimen that we have got.
（8）在no后面用that比用which普通。例如：No specimen that we have got is satisfactory.
（9）在all后面用that比用which普通。例如：Please bring me all the specimens that you have gathered. 和This is all that I know about the matter.
（10）在any后面用that比用which普通。例如：Any specimen that you may get will do. 和I have not got any that is satisfactory.
（11）在名词little和名词much后面用that比用which普通。例如：His letters contain little that is interesting but much that is dull.
（12）that用于指定的一人或多人不及who普通。例如：The man who called this morning is a professor. 和The ladies who are in the next room are his sisters. 两句里用who而不用that。但在下面各句里用that比用who普通：
- He is the best artist that has ever visited this town.
- He is the only artist that has ever visited this town.
- No artist that I know of has ever visited this town.
- Anybody that knows anything knows this.
- Who that knows anything does not know this?
- Which of us that knows anything does not know this?
- It is I that need help.
在fool that I was（像我这样的呆子）和Mrs Brown，Miss Johnson that was（Brown夫人，从前是Johnson小姐）两种表达方式里的that不可改作who。
（13）在（12）里所说的fool that I was里的fool前不可加上a或the，这语可能有两个意思。例如：
Fool that I was, I believed every word he said. （我是这样的一个呆子，竟然相信他所说的每句话。）
Fool that I was, I did not believe every word he said. （我虽然是一个呆子，我并不曾相信他所说的每句话。）
（14）用在宾格里的关系代词that往往被省去。例如：This is the book (that) I spoke of. 在口语里和若干谚语里，用在主格里的关系代词that也往往被省去。例如：
- It's not everybody (that) can do that.
- That was her shadow (that) passed the window.
- There's nothing (that) stops you from going to bed if you want to.
- It is the weather (that) makes me feel as I do.
It's an ill wind (that) blows nobody good. （谚语：1.对于任何人都吹不到好处的才是坏风。2.不论任何坏事，总有人得益。3.有弊必有利。）
（15）下面两句里的that也是关系代词：
- He has never done it(,) that I know.
- She never said anything of the kind to him(,) that I remember.
（16）下面两句语法不对：
- At the end of the passage there is a door that you may open and find someone waiting for you. （可以改作At the end of the passage there is a door that you may open to find someone waiting for you。）
- I am sending you a book that you will probably find interesting and profit by the advice it offers. （可以改作I am sending you a book that you will probably find interesting and whose advice you will profit by。）
10.以连接词that引导的从句是名词从句或状语从句，决不是形容词从句。例如：
- That he is honest is certain. （名词从句，是全句的主语）
- I hear that he is honest. （名词从句，是动词hear的宾语）
- It is a fact that he is honest. （名词从句，是It的同位语）
- I am sure that he is honest. （状语从句，修饰形容词sure）
- He is so honest that he never suspects anybody. （状语从句，修饰副词so）
不论那从句是名词从句或状语从句，必须是陈述的，决不可是疑问的、祈使的或感叹的，如下面各句都不对：
- I have to tell you that if I try, shall I have a chance to succeed? （该改作I have to ask you this: If I try, shall I have a chance to succeed? 或I have to ask you whether I shall have a chance to succeed if I try.）
- I have to tell you that if you fail, try again. （该改作I have to tell you that if you fail, you should try again.）
- I have to tell you that if you succeed, how happy I shall be! （该改作I have to tell you how happy I shall be if you succeed. 或I have to tell you that if you succeed, I shall be very happy.）
- Things happen so rapidly that who can say what may happen next week? （该改作Things happen so rapidly that no-one can say what may happen next week. 或Things happen rapidly, who can say what may happen next week.）
11.间接疑问句前面不可用连接词that，如下面各句里的that都该删去：
- He asked me that what was the matter.
- She did not know that how he did it.
- Please tell me that where he is going.
- I wonder that whether you know her or not.
12.在较长的名词从句里往往有多余的连接词that，如下面各句里斜体的that是多余的，该删去：
- It should be borne in mind that while different persons have different opinions, and that therefore they may not be able to agree upon a definite course of action, the problem is so important that it should not remain unsolved for any length of time.
- It is quite doubtful whether if he had arrived at the station five minutes earlier, or if the train had started five minutes later, that he would have caught the train.
- I suggest that while these questions are being discussed and the conditions are being investigated, that the work should be carried on as usual.
- You may rest assured that if you read any book carefully through, looking up all the difficult words and phrases and allusions in dictionaries and other reference books, dwelling upon passages of particular interest to you, and jotting down everything that you think you may have use for some day, that you will soon acquire an ability to write expressive English.
13.在定义的开首不该用连接词that，如不该说Homesickness is that one longs for one's home。
14.下面每组里的四句意思相仿，注意用may和might：
- We eat that we may live.
We eat so that we may live.
We eat in order that we may live.
We eat to the end that we may live. - He rested that he might work better.
He rested so that he might work better.
He rested in order that he might work better.
He rested to the end that he might work better.
下面几点该注意：
（1）第一组的第一句和第二句里的may在口语里往往改用can。
（2）第二组的第二句里的might可以改用should，在口语里往往改用could。
（3）第二组第三句里的might可以改用should。
15.下面各句里的以连接词that引导的从句表示结果：
- What has happened that you should weep?
- What have I done that you should be angry with me?
- Where has he been that he should look so tired?
- How have they been treated by their brother that they should speak ill of him?
- Who am I that I should advise a man of your experience?
- Am I a fool that you should tell me to share my bed with your dog?
- I wonder how you have fed the baby that he should be hungry so soon.
- He demanded to know what he had done that his wife should have asked him such queer questions.
注意：各句都是疑问句或有疑问从句。这种句子里通常有should。
16.下面各句里的that是关系副词，作when解：
- By the time that you are dressed breakfast will be ready.
- The next time that I met him was in Shanghai.
- The year that he was born was 1924.
- They left the day that we arrived.
- The moment that he saw me he ran away.
- Now that we have found it, we may take a rest.
这样用法的that往往被省去。the moment后面的that用的少，不用的多。
17.下面各句里的that是关系副词：
- He shouted with the greatest strength that he could. (that＝with which)
- They parted in the same cordial fashion that they met. (that＝in which)
- He likes sea stories for the very reason that she dislikes them. (that＝for which)
注意每句里的that所代表的...which里的介词就是那先行项前面的介词。下面两句都不对：
She was surprised at the great strength that he shouted.
I watched with interest the cordial fashion that they met and parted. 第一句里的strength前面的介词是at，但that该代表with which，不该代表at which，所以不对，该把that改作with which。第二句里的fashion前面并没有介词，所以that不对，该把that改作in which。第一句假使改作She was amused with the great strength that he shouted也不对，因为那with是跟着amused而来的，和that所代表的with which里的with不同。
18.连接词that往往被省去。例如：
- It is certain (that) he is honest.
- I am sure (that) he is honest.
- I think (that) he is honest.
- He is so honest (that) he never suspects anybody.
- It is a pity (that) you cannot come.
- It was a good thing (that) he reached home before dark.
- It occurred to me (that) you might not have heard of her death.
- I take it (that) you are going to the party this evening.
关于连接词that的省略，下面几点该注意：
（1）在口语里比在文字里省去得多，往往同一句子，把连接词that省去了便有些口语性质。
（2）在用作主语的从句的开首的that不可省去，如That he is honest is certain里的That不可省去。
（3）在用作名词的同位语的从句的开首的that通常不省去，如The fact that he is honest is known to all his friends里的that通常不省去。
（4）14里所举的每组里的第一、第三和第四句里的that不可省去。第二句里的that在英国不省去，但在美国往往省去。参见so 7
（5）15里所举的各句里的that不可省去。
（6）关于动词后面的连接词that的省略或不省略，英国人H. W. Fowler所著的A Dictionary of Modern English Usage第633页有三张表：（a）通常不省去，（b）通常省去，（c）有时省去，有时不省去，依据上下文语气而定。
(a) agree, assert, assume, aver, calculate, conceive, hold, learn, maintain, reckon, state, suggest
(b) believe, presume, suppose, think
(c) be told, confess, consider, declare, grant, hear, know, perceive, propose, say, see, understand
（7）假使省去了that意思不明白，就不该省去，如He said yesterday he had seen her可能作He said yesterday that he had seen her解，也可能作He said that yesterday he had seen her解，用了that意思就明白。
（8）即使在第一个从句里省去了that，在平行的（以and，or，nor或but引导的）从句里不省去。例如：
- He said he would come, and that he would bring his son.
- She did not believe she had ever read any of the young author's works or that she had ever heard of him.
- She did not believe she had ever read any of the young author's works, nor that she had ever heard of him.
- I think I'll have another try, but that I must have your advice beforehand.
