英语中一般的非限定性定语从句均以名词或代词为先行成分，其句中位置总是在先行成分之后。然而英语中还有一种非限定性定语从句，他们的先行成分和句中位置均不同于一般的非限定性定语从句。为求有别，我们将其称为“特殊非限定性定语从句”。例如：
（1） As we all know, he studies very hard.
（2） As is known to all, he is a promising student.
（3） He is sometimes impatient, which we teachers should never be.
（4） He couldn’t tell me, which I was anxious to know, whether the book was still in print.
引导这种特殊非限定性定语从句的关系代词一般只有as和which两个，为方便起见，下文称之为“as/which” 特殊定语从句。
一、“as/which”特殊定语从句的先行成分
1． 形容词或形容短语作先行成分
（5） Tom is always careless in his work, as we should never be.
（6） She thought his answer incorrect, which it probably was.
具有形容词意义的介词短语也可以充当先行成分：
（7） My grandmother’s house was always of great importance to me, as my own is.
在一定的语言环境里，有些名词可以具有形容词的性质。这些名词主要是那些表示人的身份、职业、状态的名词。例如：
（8） Don’t think him a fool(= foolish), which he is actually not.
（9） His grandfather was a simple-mannered man (= simple-mannered), as the large-hearted and large-minded men are apt to be.
值得一提的是，在这些具有形容词性质的名词之后，引导定语从句的关系代词不能用who/whom。试比较：
（10） a. He became an actor, as/which his parents had never expected him to be.
b. ※ He became an actor, who/whom his parents， had never expected him to be.
2． 动词短语作先行成分
这种动词短语既可是限定形式也可是非限定形式。例如：
（11） When this damned inflammation dies down, which it may be expected to do in a few weeks, I hope to get back to regular. （限定形式）
（12） When anything is offered to you, it is not polite to say “I don’t want it”, as Chinese manners would allow. （不定式）
（13） Instead of granting my request, as I had hoped, he declined it. (-ing分词)
（14） 【Beijing】 outside of actual combat, which is the ultimate flying experience, most of us old-timers stayed in the military, because we loved to fly fast airplanes. (-ing分词)
如果是动态动词短语，它们在从句中就一般有限定或非限定形式的替代动词do和as/which一起代替。do可以出现，也可以不出现，但不能用其它动词代替。试比较：
(15) a. He paid a visit to her, as he had not done for five years.
b. They say he plays truant, which he doesn’t.
c. He saw the girl, as/which he hoped he would do.
d. ※ He refused to write a dull book, as many poor writers would produce.
3. 句子作先行成分
句子可以是整个主句也可以只是主句中的一个从句。例如：
（16） The novel ends happily, which is a characteristic feature of the greater part of Dickens works.
(17) A careful observer will notice that a wire becomes thinner when it is stretched as may be seen by pulling on a piece of rubber hose.
有时作先行成分的是连续几个句子：
（18） Colin married my sister and I married his brother, which makes Colin and me double in-laws.
有时甚至可以是一个完整的故事，如我们讲完了《说谎的孩子》的故事后可以说“______ which indicates the fact that lies do harm to none other than the liar himself.”
二、“as/which”特殊定语从句在句中的位置
“as/which”特殊定语从句在句中的位置比较灵活。由于先行成分的构成成分不同，“as/which”特殊定语从句在句中的位置有以下几种情况：
1． 形容词做先行成分时
形容词或形容词短语（含具有形容词性质的名词）作先行成分，“as/which”特殊定语从句置于先行成分之后。例如：
（19） It became terribly clear in Europe, as it never had been here, that we knew more about each other than any European ever could.
（20） After leaving school, he became an artist, which his parents wanted him to be.
2. 动词短语作先行成分时
动词短语作先行成分时，“as/which”特殊定语从句置于先行成分之后。例如：
（21） Although Tianjing residents must still boil water before drinking it, as is customary throughout much of China, city residents consume 500 million litres of drinking water every day.
（22） He had neglected to occupy the strategic centers of the city, which is really the first thing to do in a revolution.
但是，当从句中含有表示主观意志的插入成分时，“as”特殊定语从句可以移至句子之首。试比较：
（23） a. She failed in the exam, as/which we believed she would.
b. As we believed she would, she failed in the exam.
3． 句子作先行成分时
句子作先行成分时，“as/which”特殊定语从句在句中的位置不尽相同。
“as”特殊定语从句的位置较灵活，可以置于先行成分之前、之中或之后。例如：
（24） a. As is reported in today’s papers, the Chinese team has won another ten gold medals in the Asian Games.
b. The Chinese team, as is reported in today’s papers, has won another ten gold medals in the Asian Games.
c. The Chinese team has won another ten gold medals in the Asian Games, as is reported in today’s papers.
但如果先行成分是直接引语，“as”特殊定语从句多在先行成分之前：
（25） As novelist George Eliot wrote more than a century ago, “Our deeds determine us as much as we determine our deeds.”
如果先行成分是否定句，“as”特殊定语从句与否定词的相对位置不同，可以使它产生不同的意义。试比较：
（26） a. He is, as you suppose, not from Beijing
   As you suppose, he is not from Beijing.
= You suppose that he is not from Beijing, and in fact, he is not from Beijing.
b. He is not, as you suppose, from Beijing.
    He is not from Beijing,as you suppose.
= You suppose that he is from Beijing, but in fact, he is not from Beijing.
由于“as”特殊定语从句具有这一特点，所以有时它的位置不能随便移动，如下例a中的“as”从句不能移至先行成分之前，b中的“as”从句不能移至先行成分之后：
(27) a. Spiders are not insects, as many people think, nor even nearly related to them.
b. As so many people say, camels are not really biting animals.
“which”特殊定语从句的位置较固定，一般在先行成分之后。试比较：
（28） a. The next letter has no date whatever, which is in itself suspicious.
b. ※Which is in itself suspicious, the next letter has no date whatever.
c. The next letter, which is in itself suspicious, has no date whatever.（语义与a、b两句不同）
在非正式的文体里，“which”特殊定语从句可以出现在先行成分之中：
（29） Marvin and Terry-which is something I’ll never understand-were quarrelling within a month of their marriage and were separated within three months.
（30） When the people looked, which was seldom, outside their own borders, England was still the dreadful enemy to be feared.
为避免语义含糊，“which”特殊定语从句有时要出现在先行成分之前。试比较：
（31） a. He went, and, which is more surprising, actually won the prize. (=He went, and, more surprisingly, he actually won the prize.)
b. He went and actually won the prize, which is more surprising. (=① It is more surprising that he went and actually won the prize./ ② He went, and more surprisingly, he actually won the prize.
（32） a. I told him, which was true, that I was proud of his acquaintance. (=I told him that I was truly proud of his acquaintance.)

b. I told him that I was proud of his acquain?蛳tance, which was true. (=① It was true that I told him that I was proud of his acquaintance./② I told him that I was truly proud of his acquain?蛳tance.)
三、“as/which”特殊定语从句的语义功能
“as/which”特殊定语从句的语义功能有同有异。一般说来，先行成分为形容词（含具有形容词性质的名词）或形容词短语时，它们的语义功能相同，即都是对先行成分作补充说明，因此一般可以相互替换。例如：
（33） He was not sick ,as/which some of the other passengers were.
（34） Mr. Smith is a kind but strict man, as/which a good teacher should be.
但先行成分为句子时，它们的语义功能则有差异。请先比较两个句子：
（35） a. He married her, as/which was natural.
b. He married her, which was disgraceful.
在这两个句子中，特殊定语从句的先行成分相同。为什么a句中的特殊定语从句既可用as又可以用which引导，而b句中的特殊定语从句则只能用which引导呢？其原因就在于这两个特殊定语从句具有不同的语义功能：a中的形容词natural呈中性，因而该特殊定语从句是对先行成分的内容加以评注； b中的形容词表结果，因而该特殊定语从句则是表明先行成分所述事实的结果。试比较：
(36) a. He married her, which was disgraceful to us.
b. He married her, which, as a result, disgraced us.
从比较中可以看出，“which”特殊定语从句既具有对先行成分加以评注的语义功能，又具有表明先行成分所述事实的结果的语义功能，而“as”特殊定语从句则只具有对先行成分的内容加以评注的语义功能。（36）b中的特殊定语从句表示结果，故不能有as引导。
表结果的特殊定语从句与其先行成分之间存在着一定的因果关系，从句中往往使用有结果意义的词，如动词result, make, enable, cause和形容词interesting, surprising, delightful, disgraceful等。例如：
（37） They lost their way, which delayed them considerably.
（38） To avoid this, you must take charge of your life—which means taking charge of your time.
（39） He admires Mrs Brown, which is surprising to me.
表示评注的特殊定语从句对其先行成分所述事实的正确性有肯定的倾向。这一点可以从下列两句的比较中看出：
（40） a. George, you said, is a liar (but I don’t believe it)
b. George, as you said, is a liar(※but I don’t believe it).
正由于表评注的特殊定语从句具有这一特点，所以它通常与那些表示客观事实、普遍真理或某种习性的先行成分连用；从句中则常用一些表示“合符自然规律”、“众所周知”或“经常发生”等意义的词语，如natural, known to all, usual等。例如：
（41） Socialist construction in China is in full swing, as/which is known all over the world.
(42) He went out for a walk after dinner, as/which was often the case with him.
(43) The day after his death all the ladies prepared to call at the house and offer condo?蛳lence and aid, as/which is our custom.
除了表结果与表评注这一语义功能差异外，“as/which”特殊定语从句之有无状语意义这一语义功能的差异：“as”特殊定语从句具有状语意义（主要是方式状语意义），而“which”特殊定语从句则无状语意义。“as”特殊定语从句的状语意义要求它在语义上与其先行成分的语义保持一致，“which”特殊定语从句则不受这种限制。试比较：
（44） a. She has married again, as/which was expected.
b. She has married again, which was unex?蛳pected.
上例a中可以用as，因为我们可以说（Just）as it was expected that she would  marry again, she has married again.
上例中b不能用as，因为我们不能说(Just) as it was unexpected that she would marry again, she has married again.
同样下面两例中的which也不能用as:
（45） He is very easy to get acquainted with, which is not a traditional English trait.
（46） A think head of hair or a hairy body was supposed to be a sign of strength, which is false.
正是由于它的状语意义，“as”特殊定语从句的位置可以移动，“which”特殊定语从句无状语意义，故它的位置比较固定。
四、关系代词as与which的句法功能
1. as/which 在特殊定语从句中做主语
as和which都可以在特殊定语从句中主语，但as做主语的情况没有which作主语普遍，这一现象与as特殊定语从句的语义功能有关。as只能在表评注的特殊定语从句中做主语，它引导的从句与其先行成分要在语义上保持一致，这些都限制了它做主语的范围，而which做主语则不受这些条件限制。例如：
（47） He was absent from the meeting, as/which is usual with him.
（48） Reports in the paper are often quoted or carried by foreign wire services, radio stations and newspapers, which is very encouraging to us.
（49） Right now I’ m me, which is why you to be you —the best, real Brett Delosanto.
另外，as做主语时，谓语动词常为连系动词（主要是be, seem）。主语补语为usual, a  rule, a matter of fact等时，系动词be习惯经常省略。例如：
（50） She has married again, as/seemed natural.
（51） As (was) usual/a general rule, they got up about six o’clock.
(52) As(is) a matter of routine, a contract must be signed by the two parties concerned before it comes into force.
（53） And, as (is the case) with all retold tales that are in people’s hearts, there are only good and bad things and black and white things and good and evil things and no in-between any?蛳where.
行为动词（常用的有announce, expect, indicate, mention, know, note, point out, say等）作“as”特殊定语从句的谓语时一般用于被动语态（其中助动词be常略）。不及物的行为动词在“as”特殊定语从句中作谓语的极少，常见的有happen一词。例如：
（54） Freddie, as might be expected, was attending the conference.
（55） As noted, many prefixes fall into this category.
（56） However, as generally happens in these cases, the elephant of the neck became involved.
Which作主语时，谓语动词不限，主语被动皆可，只是谓语动词为被动语态时助动词be省略。例如：
（57） Which the introduction of micro-tech?蛳nology, computers will operate and control entire production processes in many industries, which will result in an unacceptable level of unemploy?蛳ment.
（58） A morpheme can be defined as a minimal unit of meaning, which was mentioned previously.
As和which主语有一个共同的特点，即它们的谓语动词总是第三人称单数形式。这是因为它们代表的只是整个先行成分所表达的事实，而并非其他的东西。
2． as和which在特殊定语从句中作宾语
as和which都可以在特殊定语从句中宾语。例如
（59） At Oxford, they (Chinese students) are encouraged to use their own initiative, which they often find a bit strange to start with.
（60） I lived a long way from work, as/which you know.
（61） She was useful to him, as/which he realized.
（62） They were invited to the state banquet, which they considered a great honour.
3. as和 which在特殊定语从句中作补语
先行成分在句中作主语补语或宾语补语时，as和which都可以在特殊定语从句中作主语的补语。例如：
（63） He looked happy, as/which he was not in fact.
（64） We thought him a gentleman, as/which he could never be.
“as”特殊定语从句中可以主谓倒装，“which”从句中则不能主谓倒装。试比较：
（65） a. He was a catholic, as/※which  were most of his friends.
b. He was a catholic, as/which most of his friends were.
如果先行成分不是主补或宾补，关系代词用which而不用as。例如：
（66） He talked like a native, which/※as he hardly was.
4. which在特殊定语句中作定语
which可以在特殊定语从句中作定语，修饰fact, matter, thing 等名词。这些名词代表先行成分表达的意义，有时将其略去句义仍然完整，as不能作定语。例如：
（67） He succeeded in the experiment, which (fact/matter/thing) surprised everyone.
（68） I was told to go not by train but bus, which advice I followed.
（69） My father may have to go into hospital, in which case he won’t be going on holiday.

作者：湖南邵阳…