【简介】感谢网友“雕龙文库”参与投稿，这里小编给大家分享一些，方便大家学习。
Since从句的用法
1. Since从句为非延续性动词的过去时或现在完成时，时间的起点应该从从句动作完成时刻算起。
例如：
Things have changed a lot since I wrote to you last time.
自我上次给你写信之后，情况已发生了很大的变化。
She has lived with us since she has come here.
自从她来到这里，就一直和我们住在一起。
2. Since从句为延续性动词的一般过去时，表示动作或状态的结束。其含义与动词的词义恰好相反，具有否定意味。
例如：
All has changed since he was at home.
自从他离开家以后，这里的一切都变了。
I havent written to her since she lived in London.
自从离开伦敦以来，我还没有给她写过信。
He has never been to see me since I was ill.
自从我病愈以来，他一直没有来看我。
Two years have passed since I last smoked.
我戒烟已经两年了。
但如果since从句是延续性动词的现在完成时，则表示动作由开始延续至说话的时候，具有肯定意味。
例如：
He has never been to see me since I have been ill.
自从我生病以来，他一直没有来看我。
She has talked little since she has stayed at home.
自从她呆在家里以后，就很少讲话。
Since we have owned a car， we have gone camping every year.
自从我们有了汽车后，年年都去野营。
3. 在现代英语中，since从句是延续性动词的一般过去时，有时候也可以表示肯定意味。此时，多半用ever来加强since的语义。
例如：
She has known me ever since she was a child.
她从小就认识我了。
I have live here ever since I was born.
我生下来就住在这里。
4. 在it is+时间+since从句结构中，since从句是非延续性动词的一般过去时，含有肯定意味。
例如：
It is three years since her husband left her.
她丈夫离开她已经3年了。
It is over sixty years since the Peoples Republic of China was established.
中华人民共和国已经成立60多年了。
5. 在it is+时间+since从句结构中，since从句是延续性动词的一般过去时，含有否定的意味。
例如：
It is three years since she stayed here.
她离开这里已经3年了。
How long is it since you were a league member?
你退团有多久了?
6. 在it is+时间+since从句结构中，since从句是现在完成时或过去完成时，均含有否定意味。
例如：
It is five years since we have seen her.
我们已经5年没有见她了。
It was years since I had seen her.
在那之前，我已经有好久没有见到她了。
Its been a long time since Ive seen you.
我已经很久没有见到你了。
另外，①根据英语惯用法，since从句不可以否定形式出现。
例如：
It is four years since I have smoked a cigarette. 我已经4年不抽烟了。
不可说：It is four years since I havent smoked a cigarette.
但由于下句中的since不作自从解，所以从句可以用否定形式。
例如：
I havent been out anywhere since I dont know how long.
也不知多久了，我哪儿也没去过。
②Since从句通常不与非延续性动词的现在完成时的肯定式连用。
例如：
Her mother died when she was a child.
她小时候母亲就去世了。
不可说：Her mother has died since she was a child.
③Since前不可加表示时间的词语，但可以与ago连用。
例如：
She has lived with us since her mother died three years ago.
自从她母亲3年前去世，她就一直和我们住在一起。
不可说：She has lived with us three years since her mother died.
④在It was five years ago since his father died. 一句中的since用错了，因为在含有ago的时间范畴里，已经有了从过去的一个时间点以来的时间，即已有了since的时间范畴，所以再用since是多余的。
改为：
It was five years ago that his father died.
他父亲5年前去世了。
It is five years since his father died.
他父亲去世已经5年了。
名词从句的用法
一.主语从句
主语从句是在复合句中充当主语的从句，通常放在主句谓语动词之前或由形式主语it代替，而本身放在句子末尾。
1. It 作形式主语和it引导强调句的比较。
It 作形式主语代替主语从句，主要是为了平衡句子结构，主语从句的连接词没有变化。而it引导的强调句则是对句子某一部分进行强调，无论强调的是什么成分，都可用连词that。被强调部分指人是也可用who/whom。
例如：
It is a pity that you didnt go to see the film.
It doesnt interest me whether you succeed or not.
It is in the morning that the murder took place.
It is John that broke the window.
2. 用it 作形式主语的结构。
(1) It is +名词+从句
It is a fact that 事实是
It is an honor that 非常荣幸
It is common knowledge that 是常识
(2) it is +形容词+从句
It is natural that 很自然
It is strange that 奇怪的是
(3) it is +不及物动词+从句
It seems that 似乎
It happened that 碰巧
(4) it +过去分词+从句
It is reported that 据报道
It has been proved that 已证实
3. 主语从句不可位于句首的五种情况。
(1) if 引导的主语从句不可居于复合句句首。
(2) It is said ， (reported) 结构中的主语从句不可提前。
例如：
It is said that President Jingo will visit our school next week. (right)
That President Jiang will visit our school next week is said. (wrong)
(3) It happens， It occurs 结构中的主语从句不可提前。
例如：
It occurred to him that he failed in the examination. (right)
That he failed in the examination occurred to him. (wrong)
(4) It doesnt matter how/whether 结构中的主语从句不可提前。
例如：
It doesnt matter whether he is wrong or not. (right)
Whether he is wrong or not doesnt matter. (wrong)
(5) 含主语从句的复合句是疑问句时，主语从句不可提前。
例如：
Is it likely that it will rain in the evening? (right)
Is that will rain in the evening likely? (wrong)
4. What 与that 在引导主语从句时的区别。
What 引导主语从句时在句时在从句中充当句子成分，如主语.宾语.表语，而that 则不然。
例如：
1) What you said yesterday is right.
2) That she is still alive is a consolation.
二.宾语从句
宾语从句就是在复合句中作宾语的名词性从句，通常放在主句谓语动词(及物动词)或介词之后。
1. 作动词的宾语。
(1) 由that引导的宾语从句(that 通常可以省略)
例如：
I heard that be joined the army.
(2) 由what， whether (if) 引导的宾语从句
例如：
1) She did not know what had happened.
2) I wonder whether you can change this note for me.
(3) 动词+间接宾语+宾语从句
例如：
She told me that she would accept my invitation.
2. 作介词的宾语。
例如：
Our success depends upon how well we can cooperate with one another.
3. 作形容词的宾语。
例如：
I am afraid (that) Ive made a mistake.
That 引导的从句常跟在下列形容词后作宾语：
Anxious， aware， certain， confident， convinced， determined， glad， proud， surprised， worried， sorry， thankful， ashamed， disappointed， annoyed， pleased， hurt， satisfied， content 等。也可以将此类词后的that 从句的看作原因状语从句。
4. It 可以作为形式宾语。
It 不仅可以作为形式主语，还可以作为形式宾语而真正的宾语that 从句则放在句尾，特别是在带复合宾语的句子中。
例如：
We heard it that she would get married next month..
5. 后边不能直接跟that 从句的动词。
这类动词有Allow， refuse， let， like， cause， force， admire， condemn， celebrate， dislike， love， help， take， forgive等。这类词后可以用不定式或动名词作宾语，但不可以用that引导的宾语从句。
例如：
I admire their winning the match. (right)
I admire that they won the match. (wrong)
6. 不可用that从句作直接宾语的动词。
有些动词不可用于动词+间接宾语+that从句结构中，常见的有Envy， order， accuse， refuse， impress， forgive， blame， denounce， advise， congratulate等。
例如：
He impressed the manager as an honest man. (right)
He impressed the manager that he was an honest man. (wrong)
7. 否定的转移
若主句谓语动词为Think， consider， wuppose， believe， expect， fancy， guess， imagine等，其后的宾语从句若含有否定意义，一般要把否定词转移到主句谓语上，从句谓语用肯定式。
例如：
I dont think this dress fits you well.(我认为这件衣服不适合你穿。) 三.表语从句
表语从句在复合句中作表语的名词性从句，放在系动词之后，一般结构是主语+连系动词+表语从句。可以接表语从句的连系动词有be， look， remain， seem等。引导表语从句的that常可省略。另外，常用的还有the reason is that 和It is because 等结构。
例如：
1) The question is whether we can make good preparation in such a short time.
2) This is why we cant get the support of the people
3) But the fact remains that we are behind the other classes.
4) The reason he is late for school is that he missed the early bus.
