no, very, 等词修饰时。 3） 4）
先行词中既有人又有物时。 在there be 句型中。
关系代词和关系副词的省略 1）
可以省略。
This is the novel (that/which) I read last month. 2) 关系代词that在定语从句中作表语时可以省略。 He is not the man (that) he used to be.
3) 在there be结构的定语从句中，用作主语的关系代词that/who/which 可以省略，there is或there has ever been 等结构通常在定语从句中有 “目前有的，曾经有的”之意。
Henry was the only person (that) there was to witness the car accident. This car is probably faster than any of its kind (that) there has ever been.
4) 当先行词是reason且关系代词在句中作原因状语时，关系代词why 可以省略。 That is the reason (why) I like her so much.
5) 当先行词是way且关系代词在句中作方式状语时，关系代词in which或that可以省略。
That was the way (in which) he found out the solution to this problem. What作关系代词 1）
what用作关系代词时既可以指人，也可以指物，需注意它本关系代词which, that, who, whom在定语从句中直接作宾语时
身已包含先行词，故前面不能再有先行词。What在定语从句中可以作主语、宾语和表语。
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What has been done cannot be undone. This was exactly what my boss told me to do. 2)“ what +名词”相当于 ―all the +名词+that‖.
I have given you all what help I can.= I have given you all the help that I can. But 作关系代词： 可以引导限制性定语从句，它同具有否定意义的主句连用，其先行词可以是人也可以是物，在意义上等于 ―that/who/which…not‖。 Not a day went by but brought us bad news at that difficult time.=Not a day went by which did not bring us bad news at that difficult time. But作关系代词
But作为关系代词可以引导限制性定语从句，它同具有否定意义的主句连用，其先行词可以是人也可以是物，在意义上等于“that/who/which…not‖.
Not a day went by but brought us bad news at that difficult time.= Not a day went by which did not bring us bad news at that difficult time. There are few of us but admire your accomplishments.= Exercises: 名词性从句 分类 连接词 引导词 That, whether, if 功能 只起连接作用，不作句子成分 关系代词 Who, whom, whose, 既起连接作用，又担任主what, which, whatever, 语、宾语、定语、表语等whichever, whoever 成分 22
关系副词 When, where, how, who 1）
既起连接作用，又作状语 关系代词what 有时保留其原有的疑问意义，作疑问代词表示
“什么“；有时作双重关系代词，相当于 ―the thing that/ which‖。 I can recognize his face but I can’t remember what his name is.
His remarks reminded me of what I saw the other night in that old man’s house. 2) whether 与if 在引导名词从句时的区别：
? ?
主语从句只能由whether引导
whether or not可以连在一起用，而if or not则不可，需分开使用且or not 要放在句末；
? ? ? ? ?
whether 可以引导介词宾语从句，if 不能； 在question, ask后面一般只能用whether来引导； 后接不定式时，只能用whether;
whether 一般多用于宾语从句的肯定式，而if 引导的从句可以有否定式； 当宾语从句提至谓语前面时，只能用whether 引导。
主语从句：在句中做主语，通常位于句首。大多数主语从句都可用形式主语it代替。
如： That he survived the car accident is a miracle.=It is a miracle that he survived the car accident.
Whether he comes or not makes no difference.= It makes no difference whether he comes or not.
2) 当what引导的主语从句表示“……的东西时，whatever, whoever, whichever引导的主语从句一般不用it作形式主语。
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宾语从句 需注意的问题
1） 当宾语从句后跟有宾语补足语时，通常在宾语从句处使用形式宾语it，而将真正的宾语从句移至句末：
I think it best that you should stay here. 我认为你最好住这儿。
He hasn’t made it known when he is going to get married. 他还没宣布他何时结婚。 She found it difficult to answer the question. 她发现回答这个问题很困难。 He thought it best to be on his guard. 他认为他最好还是要警惕。
He made it a rule to speak in Parliament at least once every session. 他规定自己在议会每次开会时至少发一次言。
I consider it wrong to cheat in an examination. 我认为考试作弊是不对的。 2）宾语从句与否定转移
当动词think, believe, suppose, expect, imagine, guess, reckon, fancy, 后接一个表示否定意义的宾语从句时，其否定通常转移到主语： I don’t suppose that it is true. 我认为那不是真的。
I don’t imagine that he will come. 我想他不会来的。(from www.yygrammar.com) I don’t think we need waste much time on it. 我想我们不必在这上面花太多时间 I don’t suppose I’ll trouble you again. 我想我不要再麻烦你了。 3)．whether 与 if
引导介词宾语从句时，只能用 whether，不用if；与“or not”连用时，一般用whether，不用if。
如：I am interested in whether he'll go abroad． We don't know whether he will come or not．
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同位语从句: 一般由that引导，也可由whether或how 引导。常见的能接同位语从句的名词有： belief, opinion, hope ,idea, doubt, news, rumor, suggestion, advice, problem, order, answer, decision, conclusion, discovery, evidence, explanation, information, knowledge, law, possibility, probability, principle, truth, promise, report, thought, statement, assumption等。
例如：He put forward the suggestion that we (should) take desperate measures at once. An idea came to him suddenly that it might be his uncle that had been helping him with this project all the time. 同位语从句和定语从句的区别 从区别 同位语从句 名词性从补充说明名词 句 连接词，只起连接作用，不做任何成分 定语从句 形容词性修饰限定先行代替先行词在从句 词，描述其性质从句中充当某或特征
表语从句
1） 在系动词后，充当复合句中的表语，引导表语从句的that 通常可以省略。 It seems (that) it is going to rain. That is why Jane was praised.
That is how Mike got the first prize in the final competition.
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句 性质 功能 引导词 “that” 个成分