一、宾语从句
1)宾语从句可位于及物动词、介词和某些形容词后。连词that常可省略。介词后一般接疑问词引导的宾语从句。in that(因为),except
that(除了),but that(只是)已构成固定搭配，其他介词后一般不接that引导的宾语从句。
例句：This article is well-written except that it is a bit too long.
2)宾语从句后如有宾补，要用形式宾语it来代替，而把宾语从句移至宾补之后。
例句：He has made it clear that he would not change his mind.
3)在think,believe,suppose,expect等动词后的宾语从句中，如果谓语是否定的，一般将否定词移至主句谓语上，宾语从句则变成肯定形式。
例句：He didn't think that the money was well spent.
二、定语从句
定语从句所修饰的先行词可以是名词或代词，也可以是一个句子。定语从句通常位于先行词之后，由关系代词或关系副词引导。
1)限制性定语从句
限制性定语从句修饰先行词，对先行词起修饰作用，紧接先行词之后，无逗号，若省去，原句意思不完整。引导定语从句的关系代词有who,whom,whose,which,that等。who,whom,whose用于指人，whose有时也可指物，相当于of
which;which用于指物;that既可指人也可指物，但只用于限制性定语从句中。关系代词除了引导定语从句，替代先行词外，还在从句中担任主语、宾语、定语等。
例句：The computers and cables which make up the Internet are owned by
people
and organizations.
(1)当先行词是all,anything,everything,something,nothing等不定代词或先行词前有first,last,any,few,much,some,no,only以及形容词最高级修饰时，只能用关系代词that引导从句。
例句：That is all that I've heard from him.
(2)关系代词的省略
在从句中作宾语的关系代词常可省略。关系代词紧跟介词，作介词宾语时不可用that，只可用which或whom引导从句，并且不可省略，但当介词位于宾语从句句末时，作为介词宾语的关系代词仍可用that，也可省略。
例句：This is one of those things with which we have to put up.
(3)引导定语从句的关系副词有when,where,why等。关系副词在从句中作状语，意义上相当于一个“介词+which”的结构。
例句：Even in comic books where(=in which) there are no words,the stories
are
fully expressed through the drawings.
2)非限制性定语从句
非限制性定语从句既可修饰先行词，也可修饰整个主句，起补充说明作用，与主句之间有逗号隔开，若省去，原句意思不受影响。不可用that引导非限制性定语从句。关系词不可省略。
例句“ Every object has a gravitational pull,which is rather like
magnetism.
(1)“介词+which\whom\whose”引导的定语从句
“介词+which\whom\whose”可引导限制性定语从句，也可引导非限制性定语从句，该结构中介词的选择取决于从句谓语动词的固定搭配，或先行词的习惯搭配。
例句：This is the computer on which he spent all his savings
(2)as引导的定语从句
as引导的定语从句主要用于“such...as”及“the
same...as”的结构中，代替先行词是人或物的名词。as引导非限制性定语从句时，代替整个主句，从句可位于主句之前、之后或中间。
例句：These are not such problems as can be easily
solved.(as代替先行词problems)
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