推荐阅读：
Ⅰ. 这三个词都有“尽快、尽早”之意。
Ⅱ. as soon as 侧重于“极短时间内”。还表示“一……就……”之意，引导状语从句。如：
① I’ll return it as soon as I can.我将尽快地把它还给你。
Ⅲ. as early as 侧重于一天中的早晨或在限定的时间内再早点，以便能达到预期的目的。如：
① You should arrive there as early as you can. 你应尽早到达那里。
Ⅳ. as quickly as 表做某事的速度非常之快或动作非常之敏捷。如：
① Please read the text as quickly as you can. 请把课文尽快读一遍。
§47 as soon as/ hardly…when/ no sooner…than
Ⅰ. 三者在意义上基本相同，都有“一……就……”，“刚……就……”，但它们各有其特点。
Ⅱ. as soon as 最为普通，位置灵活，可在主句前，也可在其后。且可用作多种时态。如：
① As soon as I went in , Kate let out a cry of surprise. 我一进去，凯特就惊讶地叫了一声。
② I’ll tell him as soon as he comes back.
Ⅲ. hardly… when…的主句通常 用过去完成时，从句用一般过去时，when有时还可换成before.如：
① He had hardly finished his homework when the light went out. 他刚写完作业灯就灭了。
② Hardly had I come back when they began quarrelling.我一回来他们就开始吵了起来。(hardly 提前时，句子需要倒装。)
Ⅳ. no sooner…than…句型中， no sooner一般只置于句首，所以主句有倒装形式。如：
No sooner had I known the news than I telephoned my mother. 我刚知道这个消息就打电话告诉了妈妈。
§48 as well as/ as well
Ⅰ. as well as “也”“不仅…而且”意同：not only … but also具有连词性。
① She is my friend as well as my doctor. 他不仅是我的医生，也是我的朋友。
② Small towns as well as big cities are being industrialized. 小城市与大城市一样都在迅速实现工业化。
Ⅱ. as well “也”具有副词性。大致相当于also 或 too . 如：
He can speak Chinese as well.
§49 as/ because/ for/ since
Ⅰ. 这三个词都可以用作连词，表“原因、理由” 但有区别：
Ⅱ. as “因为、既然”表示的原因或理由是明显的。语意不如because强。当理由是明显的，或者被认为是已知的时，则以用as 为好。如：
① As he was not well, I decided to go without him. 因为他身体不好，我决定独自去了。
② As it was getting very late, we soon turned back. 因为已很晚了， 我们很快就回来了。
③ As it is raining, you’d better take a taxi. 既然在下雨，你最好乘出租车。
Ⅲ. because “因为”表直接而明确的原因或理由。即必然的困果关系。在这几个词中，它的语意最强。回答以why 引导的特殊疑问句时，只能用because . 注意：because 不可以与so 连用。如：
① He had to stay at home yesterday because he was ill.昨天他只得呆在家里，因为他病了。
② I did it because they asked me to do it. 我之所以做这件事，是因为他请我做的。
③ ---Why can’t you do it now? --- Because I’m too busy.
Ⅳ. since“既然”比as 较为正式，说明为人所知的原因。语气比because 稍弱。
① Since light travels faster than sound, we see lightening before we hear the thunder.因为光比声音传播得快，所以我们先看到闪电，后听到雷声。
② Since he can’t answer the question, you’d better ask someone.既然他回答不了这个问题，你最好问别人吧。
③ Since you are busy, I’ll do it for you.既然你忙，我替你做吧。
Ⅴ. for “因为”表原因或理由时，用以说明理由，只是解释性的。在这几个词中，它的语意最弱。它少用于口语中，也不用于句首。如：
① I asked her to stay to tea, for I had something to tell her. 我请她留下来喝茶，因为我有事要告诉她。
② We must get rid of carelessness, for it often leads to errors. 我们一定克服粗枝大叶的毛病，因为粗枝大叶常常差错。
③ It must have rained, for the road is wet. 一定下雨了，因为路是湿的。
④ I must go now, for my sister is waiting for me. 现在我得走了，我姐姐在等我呢。
[注]：这几个词按语意的强弱来排，其顺序为：
because—→since—→(as)—→for
§50 as/ when/ while
这三个词都可以用作连词，表时间关系， 但有区别：
Ⅰ. as “当(在)……时候”往往可与when 或 while 通用，但它着重指主句和从句的动作或事情相并发生。如：
① I saw him as he was getting off the bus. 当下公共汽车的时候，我看见了他。
② As he walked on, he felt himself getting more and more tired.他继续往前走的时候，感到越来越疲乏。
Ⅱ. when “当(在)……的时候”主句和从句的动作或事情可以同时发生，也可以先后发生。
① It was raining when we arrived. 当我们到达的时候，正下着雨。
② When we were at school, we went to the library every day. 我们在求学的时候，每天都到图书馆去。
Ⅲ. while “当(在)……的时候”表主句的动作或事情发生在从句中的动作或事情的进展过程之中。从句通常为进行时态。它有时可与when通用，但它只能指一段时间(a period of time),而不能指一点时间(a point of time)如上面的第一个例子。又如：
① Please don’t talk so loud while others are working. 别人在工作的时候，请勿大声讲话。
② While I am washing the floor, you can be cleaning the windows.我洗地板时，你可以擦窗户。
