引导语：关系代词as引导定语从句时，既可以单独使用，也可以与其它词连用，其用法要比that和which更为复杂，值得注意。现将其归纳如下。
as引导定语从句与其它词连用
A．用于the same．．．as．．．结构中
This is the same sickle as I lost yesterday．这把镰刀和我昨天丢的那把一样。
We drove out of the town by the same road as we had entered by．我们沿着进城的同一道路开车出城。
This is the same material as is used in building the bridge．这和建那座桥所用的材料一样。注意：在这一结构中，as有时可以由that代替。例如：
I live in the same district as／that he lives in．我和他住在同一区。但两者亦有区别：
1．当定语从句省略谓语部分时，要用as。例如：
She uses the same scent as you（do）／that you do．她用的香水和你的一样。
This book of his is the same as yours．他的这本书和你的那本一样。
2．在容易引起歧义时，慎用as和that。例如：
This is the same knife as I lost last week．（一般理解为：这把刀和我上周丢的那把相似。也可理解为：这是我上周丢的那把刀。）
This is the same knife that I lost last week．这是我上周丢的那把刀。
3．that在现代英语中可作关系副词，而as则不可。例如：
I live in the same district that he lives．（不可用as。）
B．用于such．．．as．．．结构中
I never heard such stories as he tells．我从未听过像他讲的那种故事。
He was in such a fury as I've never seen．他怒气之大，我从没见过。
Such women as knew Tom thought he was charming．认识汤姆的`女人都认为他很有魅力。注：有时such和as连在一起用。例如：
We had hoped to give you a chance such as nobody else ever had．我们本希望给你一次别人不曾有过的机会。
We are living in a new era such as has never existed before．我们生活在前所未有的新时代。
C．用于“so＋adj．＋a（n）＋n．（单数）＋as结构中
We witnessed so great a parade as nobody ever dreamt of in preliberation days．我们见到在解放前没有人曾经梦想过的一次盛大的。
I'm not so strong a man as I was．我已不像从前一样健康了。
He's never written again so good a book as his first one．他再也没写出像他的第一部那么好的书。
D．用于“as＋adj．＋n．＋as比较结构中
He is as learned a professor as works in the uni- versity．他是在这所大学工作的教授中最有学问的一个。
Some people have no doubt that their cat understands as many words as does a dog．许多人相信他们的猫跟狗懂的话一样多。
They are as fine women as ever walked．她们可以与任何卓越的女性媲美。注：as．．．as．．．后面加上ever以加强语气，表示“不亚于任何……”，“不弱于……”，有最高级的意味。又如：
He is as brave a man as ever lived．他是世界上最勇敢的人。二、as单独引导定语从句
A．as单独引导定语从句时，先行词可以是一个词，但更为常见的是：它的先行词是整个主句，有时也可以是一个短语。例如：
The two brothers were satisfied with this decision，as was agreed to beforehand两兄弟对此决定都很满意，这项决定事前已得到他们的同意。（先行词是decision）
She is late，as is often the case．她迟到了，这是经常的事。（先行词是整个主句）
He married her，as was natural．他和她结婚了，这是很自然的。（先行词是整个主句）
To shut your eyes to facts，as many of you do，is foolish．视而不见———你们好多人都是如此———是愚蠢的。
