as的用法
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.你的鋼筆書寫起來和我的一樣流暢。
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的常見句型：
(1)as...as possible
Please answer my question as soon as possible.請(qǐng)盡快回答我的問題。
(2)as...as usual/before
She looks as pretty as before.她看起來和以前一樣漂亮。
(3)as long as... (引導(dǎo)條件狀語從句)
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)的常見短語歸納：
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)間狀語從句
as與when，while都是引導(dǎo)時(shí)間狀語從句的從屬連詞，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)而越來越聰明。
3. as用作連詞引導(dǎo)原因狀語從句
as，because，since都可以表示因果關(guān)系，連接原因狀語從句，含義是"因?yàn)�，由�?quot;，但它們有區(qū)別：because表示的語氣最強(qiáng);as一般放在句首，語氣較弱，較口語化;since常常用在書面語中，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^雨，空氣比較清爽。
4. as作連詞引導(dǎo)讓步狀語從句
as與although (或though)，however (或no matter how)等都可以引導(dǎo)讓步狀語從句，含義是"雖然，盡管"，但它們有區(qū)別：although語氣稍正式些，可放在句首，也可放在句中，主句中不能再用but，但可以用yet;as所表示的語氣較強(qiáng)，引導(dǎo)的讓步狀語從句用倒裝語序;however引導(dǎo)讓步狀語從句時(shí)，它的后面可跟形容詞或副詞，也要用倒裝語序。例如：
(1) Although he is quite old, he still jogs every day.他雖然年紀(jì)相當(dāng)大，仍然每天慢跑。
(2) Strange as it may seem, nobody was injured in the accident.這次意外雖然顯得令人不可思議，卻沒有人受傷。
(3) However hard he may try, he will not attain his goal.無論他怎樣努力也達(dá)不到目標(biāo)。
二、as作關(guān)系代詞的用法
關(guān)系代詞as引導(dǎo)定語從句時(shí)，既可以單獨(dú)使用，也可以與其他詞連用，其用法要比that和which更為復(fù)雜。
1. as引導(dǎo)定語從句與其他詞連用
�、儆糜趖he same...as結(jié)構(gòu)中
This is the same book as I read last week.這本書和我上周讀的那本是一樣的。
�、谟糜趕uch...as結(jié)構(gòu)中
I don”t like such books as he recommends.我不喜歡他推薦的那些書。
�、塾糜�"so +adj. + a/an + n. (單數(shù)) + as "結(jié)構(gòu)中
I am not so strong a man as I was.我已經(jīng)沒有從前那么強(qiáng)壯了。
2. as單獨(dú)引導(dǎo)定語從句
as單獨(dú)引導(dǎo)定語從句時(shí)，先行詞可以是一個(gè)詞，也可以是一個(gè)句子或短語。例如：
(1) She is late, as is often the case.她遲到了，這是經(jīng)常的事。(先行詞是整個(gè)主句)
(2) To shut your eyes to facts, as many of you do, is foolish.對(duì)事實(shí)視而不見--你們好多人都是如此的愚蠢。(先行詞是不定式短語)
三、as作介詞的用法
as作介詞，意思是"作為"，"以……身份"。例如：
He came to China as a tourist five years ago.他五年前以游客的身份來過中國(guó)。
四、as作副詞的用法
to the same degree or amount; equally "相同地"，"同樣地"。例如：
They don”t have as many airplanes.他們沒有同樣多的飛機(jī)。
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