替代 (Substitution) 是一种避免重复和连接上下文的手段。对句子中相同的非关键性词语可用替代词来替代，从而达到避免重复的目的, 使文字更加精练，英语中的替代情况主要有以下三种：名词性替代、动词性替代和分句性替代。此外还有状语的替代。
用名词性替代词one(s), the same, the kind, the sort等所表示的替代现象叫做名词性替代。
The child doesn’t like this book. Show him a more interesting one. (one = book)
His novel is a bad one for children. (one = novel)
在名词性替代中还可以用一些不定代词来替代。如all, both, some, any, enough, several, none, many, much, more, (the) most, (a) few, another, the other, others, either等。
I don't want any more food. I’ve had enough.
3．one 和 ones 是最常见的替代词
one的复数形式是ones. one 和ones作为替代词只能用以替代可数名词，不可用来替代不可数名词。
The grey horse is stronger than the black one.
The new design is much better than the old ones.
名词性物主代词mine, yours等可用来代替my +名词，your +名词等，
“Whose is that coat?” “It’s mine.”
Some people like a shower after they have played tennis. Peter does, for example.
John speaks German as fluently as Mary does.
“Mary will enter the university in September.” “So will Joan.”
“I’ve been to Beijing.” ”So you have.”
（3）“主语+（助动词+）do + so”。例如：
“Have you sent your plan to the committee?”
“I did so yesterday.”
（4）“主语+（助动词+）do + that”。例如：
“Do you know who broke the television set?”
“I heard John did that.”
（5）“主语+（助动词+）do + it”。例如：
“My brother said he was going to send a letter of protest to the President.” ”I did it last week.”
注：如果上文表示否定意义而在简短反应中表示相同的看法时，则用“neither / nor +do +主语”。此时，do 不是动词替代词，而是助动词。例如：
Mary didn’t like English, neither did her brother.
I went there because I wanted to. (=…because I wanted to go there.)
Perhaps I’ll go to Brazil this summer; I’d very much like to.
“Are you and Gillian getting married?” ”We hope to.”
I think he should get a job, but you can’t force him to if he’s not ready (to).
I don’t dance much now, but I used to a lot.
We’ll never leave home; he hasn’t got the courage (to).
“Can you start the car?” “Ok, I’ll try.”
注2：在want和would like之后，通常不能省略to。然而，当want或like 用于从句时（例如，在when, if, what, as之后），to常常省略。例如：
Come when you want.
I’ve decided to do what I like.
Come and stay as long as you like.
Many people believe that there will be another world war before the end of the century. My father think so, but I believe not.
so可用来替代肯定的that从句，not替代否定的that从句，它们常与I’m afraid, believe, expect, fear, guess, hope, suppose, think等词语搭配。
“Have we got enough money?” “I think so.”
“We’re not going to be in time.” “No, I suppose not.”
Are you free this evening? If so, come and have a drink with us.
Are you busy this afternoon? If not, I wish you would stay with me for a while.
3．用it, this, that, such作为替代词
If you don’t work hard, you’ll regret it. (regret it = regret not working hard)
He was very tired. This explains why he went to bed early.
You’re trying to cut with the back of the knife; that’s a silly thing to do.
I may hurt your feelings, but such (= that) was certainly not my intention.
We saw John at eight on Monday evening. We told him then that we could be coming to the party.
Mary is in London and John is there too.
They sat right in front of the stage. That / it / There was where the noise was greatest.
3．方式状语的替代形式用in that way和like that
“She plays the piano with great concentration and with great energy.” “I’m afraid she doesn’t study like that.”