非限制性定语从句的概念：

非限制性定语是对被修饰名词或代词的附加说明，它不是必需的，如果去掉，也不会影响句子的意思，它与被修饰名词之间通常用逗号分开。
如：The travellers, knowing about the floods, took another road. 游客们知道发了大水，都改道走了。
        The boys, wanting to play football, were disappointed when it rained. 那些男孩子想踢足球，因为下雨感到失望。

非限制性定语从句用法：

1、引导非限定性定语从句时，只能用which(不用that)。
例如：Heat is another form of energy, which is as important as other kinds of energy.
            热是另一种形式的能量，与其他形式的能量一样重要。 （从句表补充说明，而且关系代词which不能换成that。） 　　
2、引导非限定性定语从句的which可以指代前面的先行词,也可以指前面整个句子的含义。
例如：That Peter will marry Alice, which has not been announced yet, has spread around.
            彼特要娶爱丽斯这件事还没宣布，却已传得沸沸扬扬。（句子中的which指“彼特要娶爱丽斯”这整个句子的意思。） 　　
3、除which外，还可用when，where，who等关系代、副词引导非限定性定语从句。
例如：After graduation, I decided to stay in Chongqing, where I spent my childhood and four years of college life. 
毕业后，我决定留在重庆，在那里我曾度过了我的童年和四年大学生活。 　　                 
Albert Einstein left Germany for the United States during World WarII, when Jews were badly treated in Germany.  
第二次世界大战期间，爱因斯坦离开德国去了美国，那时犹太人在德国受到不好的对待。 　　
4、在限定性定语从句中作宾语时，引导词可以省略，但引导非限定性定语从句的关联词不能省。
如：He was eager to go to the hospital to see his stepmother, whom he loved and respected as his own mother. 
他急于想去医院看望他的继母，他把他的继母当作亲生母亲一样热爱和尊敬。 　　    
The American journalist(whom/who) the announcer mentioned in the news broadcast is said to have been killed by the gangsters.
 播音员在新闻广播中提到的那位美国记者据说已经被匪徒杀害了。 　　
两例中的关系代词都在从句中作宾语。由于第二例是限定性定语从句，可以省略关系代词；第一例中的引导词不能省略，因为它引导的是非限定性定语从句。 　　
5、表示“正如”的含义时，通常用as引导非限定性定语从句，也可用which引导；但置于句首时，只能用as引导。 　　
如：China has basically succeeded in defeating SARS, which/as we have expected.
        正如我们所预料的那样，中国已基本上战胜了“非典”。 　　  
        As is well known to everybody, Tai wan is an inseparable part of China.
        众所周知，台湾是中国不可分割的一部分。 　　
但是当非限定性定语从句是否定含义时，就只能用which(而不用as)引导。
如：He didn't win the championship, which I hadn't expected.
        他没获得冠军，这一点是我没预料到的。

非限制性定语丛句中as, which的区别：

1、which引导非限制性定语丛句代表前面的整个句子的时候，一般是对主句的结果的说明。 
      如： He grows too fast, which makes him taller than his classmates.
2、as引导非限制性丛句代表前面整个句子时一般来讲丛句的谓语动词有三种：
A. 含有be动词：
如：He failed the exam, as is natural.
B. 实意动词的被动形式：
如：As is reported, the fire caused a great loss.
C.感官动词和意识类动词如：
如：see, hear, notice, know, learn, realize 等。 
        As you know, I am a teacher.
3、as可翻译为正如，它引导的丛句可位于主句之前，也可位于主句之后；which引导的该丛句只能位于主句之后。
例1：__A___he realized, I was very useful to him. 
例2：This elephant is like a snake, ___A__anybody can see. 
例3：The sun gives us light and heat, __B___makes the plan tgrow well.
          A. As(as)
          B. which
          C. that
          D. who

限定性定语从句与非限定性定语从句的区别：

非限制性定语从句的关系词：

非限定性定语从句的使用规则及注意事项：

1、which引导的非限定性定语从句是用来说明前面整个句子的情况或主句的某一部分。
2、在引导限定性定语从句时，that有时相当于in which, at which, for which或at which。其中，介词的选用，依据从句中的动词所需搭配的介词来选用。例句：
① Attitudes towards day dreaming are changing in much the same way that(inwhich)attitudes towards night dreaming have changed.
    人们对白日做梦的态度正在改变，这与人们对夜间做梦的看法的变化有非常相似之处。
② I like the music for the very reason that(for which) he dislike it. 
    我出于某种原因喜欢这种音乐，而他恰恰与我相反。
③ We arrived the day that(on which) they left.
    刚好我们到的那天他们走了。
3、as有时也可用作关系代词。
4、在非限定性定语从句中，关系词不能用that。

there be句型的概念：

英语中的there be结构主要表示某处存在有某物，所以通常被称为存在句。其中的there为引导词，无词义，be为谓语动词，therebe后面的名词为句子主语。

therebe结构的否定式和疑问式：

 1、否定式：
there be结构的否定式通常应将否定词置于动词be之后：
如：There is not any bread left. 没有一点面包了。
        There isn't anything I can do for you. 我帮不了你什么忙。
若谓语中包括有助动词或情态动词，通常将否定词置于助动词与情态动词之后：
如：There can't be so many mistakes. 不可能有那么多错误。
        There shouldn't be any doubt about it. 对此不应有什么怀疑。
        There haven't been any parties in weeks. 好几个礼拜没开过晚会了。
另外注意以下类型的否定式：
如：There doesn't seem to have been any difficulty over the money question. 在钱的问题上似乎没发生什么困难。
2、疑问式：
there be结构的疑问式通常应将否定词置于动词be之后：
如：Is there any good film on? 映什么好电影吗?
        Is there room for me in the car? 车子里还有我坐的地方吗?
        Are there any letters for me? 有我的信吗?
若谓语中包括有助动词或情态动词，通常将助动词或情态动词移至句首构成疑问式：
如：Has there been an accident? 出事了吗?
        Have there been any new developments? 有什么新的发展吗?
        Can there have been so much rain there？那儿会下过那么多雨吗？
另外注意以下类型的疑问式：
如：Uncle Jesse, why do there have to be poor people like those? 杰西叔，为什么一定要有他们那样的穷人?

there be结构的谓语形式：

1、主谓一致问题：
 若只有一个主语，谓语的数则取决于该主语的数；若有几个主语并列，则通常是与靠近的主语保持一致：
如：There is a man at the door. 门口有个人。
        There are some girls in the room. 房间里有几个女孩。
        There is a pen and some books on the desk. 桌上有一支钢笔和一些书。
2、时态问题：
there be结构的时态由其中的谓语动词be来体现，它可以有一般现在时、一般将来时、一般过去时、现在完成时以及过去完成时等多种时态形式：
如：There is going to be[will be] an English film tonight. 今晚将有一场英语电影。
        There was a lot to be done. 有很多事要做。
        There were some children swimming in the river. 有些小孩在河里游泳。
        There have been many such accidents. 已发生了好几起那样的事故。
        There had been two seafights between them. 他们之间发生了两场海战。
3、与情态动词连用：
there be结构有时可以与情态动词连用：
如：There may be a storm tomorrow. 明天可能有风暴。
        There used to be a hospital here. 原来这里有家医院。
        He felt there must be something wrong. 他感到准有什么问题。
        There might still be hope. 可能还有希望。
        There ought to be a comma here. 这儿应有一个逗号。
4、动词be换成其他动词：
有时可将there be中的动词：be换为live, remain, seem, appear, exist, stand, lie, come等：
如：Once upon a time there lived a man known by the name of Joe Beef. 从前有个人名叫乔·比夫。 
        There seems[appears] something the matter with her. 她好像是出了什么事似的。
        There existed different opinions on this problem. 对这个问题曾有不同看法。
        There remained just twenty-eight pounds. 只剩28英镑了。
        At the top of the hill there stands an old temple. 在小山顶上有一座古庙。
5、与其他动词搭配使用：
there be结构有时可与其他动词搭配使用，构成一种复合谓语：
如：There seemed to be nobody about, so I went in. 附近似乎没有人，因此我就走了进去。
        There happened to be a man walking by. 恰好有一个人从旁经过。

therebe结构的非谓语形式：

基本结构：there be结构的非谓语形式有两种基本结构，即there being和there to be：
1、there being结构该结构的主要用法有：
(1)用作状语：
如：There being nothing else to do, we went home. 由于没什么其他的事要干，所以我们就回家了。
        There having been no rain, the ground was dry. 由于没有下雨，所以地面很干。
【注】有时可与状语从句转换：
如：There being no further business(=As there was no further business), I declared the meeting closed. 由于没有别的事了，我宣布闭会。
(2)用作介词宾语：
如：There is now some hope of there being a settle ment of the dispute. 现在有点希望可以解决这次争端。
2、There to be结构该结构的主要用法有：
(1)用作动词宾语：该结构可用作某些动词（如like, prefer, hate, want, mean, intend, expect, consider等）的宾语：
如：I don't want there to be any misunderstanding. 我可不希望有任何误解。
        Students hate there to be too much homework. 学生讨厌做太多的家庭作业。
        We expect there to be more discussion about this. 我们期望能对此展开更多的讨论。
【注】在let there be结构中，动词be不带to：
如：Don't let there be any noise. 不允许有任何吵闹。
        Let there be no mistake about it. 这事不要出错。
(2)用作介词for的宾语：
如：They asked for there to be another meeting. 他们要求再开一次会议。
【注】用作介词宾语一般用there being，但用作介词for的宾语时，只能用there to be。
比较：They planned on there being another meeting. 他们打算再开一次会议。
            They planned for there to be another meeting. 他们打算再开一次会议。

几个重要句型和结构：

 1、There is no doing结构：
其意为“不可能…”、“无法…”：
如：There's no denying the fact. 这一事实不容否认。
        There is no getting over the difficulty. 这困难无法克服。
        There is no knowing what he will do next. 无法知道他下一步要干什么。
        There was no telling when she would be back. 没法知道她什么时候回来。
2、There is no difficulty in doing sth结构：
意为“做某事没有困难”：
如：There is no difficulty in finding his office. 找到了他的办公室没费一点劲。
        There was no difficulty in carrying out the plan. 执行这项计划没什么困难。
3、There's no doubt…结构：
意为“毫无疑问…”：
如：There is no doubt of his success. 毫无疑问他一定会成功。
        There could be no doubt that he was one of the best writer in this country. 毫无疑问他是这个国家最优秀的作家之一。
4、There is no hurry(to do sth)句式：
其意为“不用急(于做某事)”：
如：There's no hurry to return the book. 现在不急于还书。
        There's no hurry, so do it slowly and carefully. 不用赶时间，要慢慢细心地做。
5、There's no need for…结构：
其意为“不需要或不必要…”：
如：There is no need for help. 不需要帮助。
        There is no need for you to go. 你没有必要去。
6、There is no question about...结构：
其意为“…是毫无疑问的”：
如：There's no question about his success. 毫无疑问他会成功。
        There's no question about his honesty. 毫无疑问他是诚实的。
7、There is no question of doing sth句式：
其意为“做某事是不可能的”：
如：There is no question of his coming. 他不可能会来。
        There is no question of our arriving on time. 我们不可能准时赶到。
8、There is no sense in doing sth结构：
意为“做某事没有道理或好处”：
如：There's no sense in criticizing him. 批评他也没有用。
        There's no sense in waiting three hours. 等三小时是不没有道理的。
9、There's no point in doing sth句式：
意为“做某事没有用”：
如：There's no point(in) telling her about it. 告诉她没有用。
如：There's no point in wasting time. 耗时间没用。
【注】以上有的结构中的no根据情况也可换成其他限定词：
如：There is some difficulty in doing sth 意为“做某事有些困难”。 
        There is much difficulty in doing sth 意为“做某事许多困难”。
        There's a need for… 意为“需要或有必要…”。
10、“there be＋名词＋动词”结构：
（1）there be+宾语+现在分词现在分词表示主动关系，同时表示动作正在进行：
如：There is some one waiting for him. 有人在等他。
        There was a man standing in front of me. 我前面站着一个男人。
        There were some children swimming in the river. 有些小孩在河里游泳。
        There were a group of young people working in the fields. 有一群青年在地里劳动。
有时现在分词可表示一种状态：
如：There's a piano standing against the wall. 靠墙有一架钢琴。
        There're a lot of difficulties facing us. 我们面前有很多困难。
        There is a door leading to the garden. 有一座门通往花园。
有个别现在分词用于该结构时可以表示将来(正如它们可用进行时表示将来一样)：
如：There are ten people coming to dinner. 有10个人来吃晚饭。
（2）there be+宾语+过去分词过去分词表示一种被动关系，同时表示动作已经发生：
如：There is nothing written on it. 上面没写东西。
        There were ten people killed in the accident. 事故中有10人丧生。有时过去分词也可表示一种状态(可转换成被动结构)：
        There were some old men seated(=who were seated)in the back. 有些老人坐在后面。
        There is a red car parked(=which is parked)outside the house. 房子外边停着一辆红色汽车。
（3）therebe+宾语+不定式不定式通常表示动作尚未发生：
如：There was nobody to look after the child. 没有人照顾这孩子。
        There was a large crowd to send him off. 有一大群人要来给他送行。
        There was so much to lose that we couldn't take any risks. 可能会有很大的损失，因此我们不能冒险。
【注】当其中的宾语与其后的不定式为被动关系时，可用主动表被动，也可用被动式：
如：There is much work to do[to be done]. 有许多工作要做。有时其中的不定式为系表结构：
        There is nothing to be afraid of. 没什么可怕的。
        What was there to be afraid of. 有什么可怕的?
        There's nothing to be ashamed of. 没有什么值得羞愧的。