一、as作連詞的用法
1. as...as的用法
as...as意為"和……一樣"，表示同級(jí)的比較。使用時(shí)要注意第一個(gè)as為副詞，第二個(gè)as為連詞。其基本結(jié)構(gòu)為：as+ adj./ adv. +as。例如：
(1)This film is as interesting as that one.這部電影和那部電影一樣有趣。
(2)Your pen writes as smoothly as mine.你的鋼筆書(shū)寫(xiě)起來(lái)和我的一樣流暢。
其否定式為not as/so +adj./ adv. +as。例如：
This dictionary is not as/so useful as you think.這本字典不如你想象的那樣有用。
若有修飾成分，如twice, three times, half, a quarter等，則須置于第一個(gè)as之前。例如：
Your bag is twice as expensive as mine.你的袋子比我的貴一倍。
幾個(gè)關(guān)于as...as的常見(jiàn)句型：
(1)as...as possible
Please answer my question as soon as possible.請(qǐng)盡快回答我的問(wèn)題。
(2)as...as usual/before
She looks as pretty as before.她看起來(lái)和以前一樣漂亮。
(3)as long as... (引導(dǎo)條件狀語(yǔ)從句)
It took us as long as three years to carry out the plan.我們花了長(zhǎng)達(dá)三年的時(shí)間才完成這項(xiàng)計(jì)劃。
(4)as far as
He walked as far as the railway station yesterday evening.昨天傍晚，他一直散步到火車(chē)站。
(5)as well as
She cooks as well as her mother does.她燒菜燒得跟她母親一樣好。
一些帶有as...as結(jié)構(gòu)的常見(jiàn)短語(yǔ)歸納：
as busy as a bee像蜜蜂一樣忙碌
as easy as ABC像ABC一樣容易
as deep as a well像井一樣深
as light as a feather像羽毛一樣輕
as soft as butter像黃油一樣軟
as rich as a Jew像猶太人一樣富裕
2. as用作連詞引導(dǎo)時(shí)間狀語(yǔ)從句
as與when，while都是引導(dǎo)時(shí)間狀語(yǔ)從句的從屬連詞，含義都是"當(dāng)……的時(shí)候"。但它們有區(qū)別：用when時(shí)，從句的動(dòng)作可以與主句的動(dòng)作同時(shí)發(fā)生，也可以先于主句的動(dòng)作發(fā)生;用while時(shí)，從句的動(dòng)作為一過(guò)程，主句動(dòng)作與從句動(dòng)作同時(shí)進(jìn)行或在從句動(dòng)作過(guò)程中發(fā)生;用as時(shí)，主句和從句的動(dòng)作同時(shí)發(fā)生，具有延續(xù)的含義。例如：
(1)It was snowing when he arrived at the construction site.他到達(dá)工地時(shí)，天正在下雪。
(2)He was watching TV while his mother was cooking.他母親做飯時(shí)他在看電視。
(3) You will grow wiser as you grow older.你會(huì)隨著年齡的增長(zhǎng)而越來(lái)越聰明。
3. as用作連詞引導(dǎo)原因狀語(yǔ)從句
as，because，since都可以表示因果關(guān)系，連接原因狀語(yǔ)從句，含義是"因?yàn)�，由�?，但它們有區(qū)別：because表示的語(yǔ)氣最強(qiáng);as一般放在句首，語(yǔ)氣較弱，較口語(yǔ)化;since常常用在書(shū)面語(yǔ)中，表示多為對(duì)方已知的、或稍加分析便可得知的原因，有時(shí)可譯作"既然"。例如：
(1) He will succeed because he is in earnest.他一定會(huì)成功，因?yàn)樗苷J(rèn)真。
(2) Since you are so sure of it he”ll believe you.既然你對(duì)此如此有把握，他會(huì)相信你的。
(3) As rain has fallen, the air is cooler.因?yàn)橄逻^(guò)雨，空氣比較清爽。