你首先要搞清楚限制性定語從句和非限制性定語從句的區(qū)別,然后再把a(bǔ)s的用法搞清楚,這樣才能知道他們的可比性.s……as
AS +adj(原級)+AS
AS +adv(原級)+AS
as soon as 一……就
as soon as possible 盡可能快地
as early as possible 盡可能早的
as carefully as you can 盡可能認(rèn)真地
as careful as you can 盡可能認(rèn)真的
1.as是連詞,表示“隨著”的意義.lives是life的復(fù)數(shù),意義是“生活”.

2.as是連詞,表示“因?yàn)?由于”的意義.wanting是現(xiàn)在分詞,表示主動意義,wanting to buy cars=who want to buy cars.
As的用法小結(jié)
as可以作連詞、介詞及關(guān)系代詞和副詞.現(xiàn)將其用法小結(jié)如下:
（一）、 as作連詞的用法:
1.作“在-------期間,當(dāng)----的時(shí)候”引導(dǎo)時(shí)間狀語從句.注意與when、 while的用法區(qū)別.
①下列情形時(shí),只用as, 而不用when或while.
1)用于表示同一個人的兩種動作交替進(jìn)行,指一邊----一邊. 如:
The girl sings as she goes to school.
He looked behind occasionally as he went forward in the forest.
2)表示兩個同步發(fā)生的動作或行?意思是隨著-----的發(fā)展.如:
As time went on / by, she became more and more beautiful .
As children get older, they become more and more interested in everything.
3)表示兩個短暫行為或事情幾乎同時(shí)發(fā)生.如:I watched her as she read the book.
I thought of it just as you opened your mouth.
Just as the flying worm hit her face, she gave a loud cry.
4)接在名詞后面表示某一個年齡段時(shí).如:
As a young man, he was active in sports.
②when作"當(dāng)……的時(shí)候"解,可以指較短的(一點(diǎn))時(shí)間,也可指一段時(shí)間.如:When I was at college, I could speak several foreign languages. When the clock struck twelve, I had slept for 2hours.
③ while常表示一段較長的時(shí)間或一個過程,強(qiáng)調(diào)主句謂語動詞與從句謂語動詞同時(shí)發(fā)生.如:Work while you work. Play while you play.
2. As =Since 作"既然"、"由于"解,引導(dǎo)原因狀語從句,常用來表示已為人們所知或顯而易見的原因或理由.如: As he’s been ill for ages, I will help him.
As / Since you're not feeling well, you may stay at home.
As he wasn't ready , we went without him.
3. As =in the way that作"像"、"按照……的方式"解,引導(dǎo)方式狀語從句.如:
Do as I told you.
Remember, you must do everything as I do.
4. 用于as--- as或not / so/ as ---- as中,前一個as是副詞,后一個as是連詞,引導(dǎo)比較狀語從句.如:They helped the old as much as possible.
I don't speak English so/ as well as she does.
5. 表示雖然,盡管 等,引導(dǎo)讓步狀語從句,常用倒裝語序,模式為:
adj. /adv. / n.+as +主語+謂語+主句.如: Young as he is, he knows much.
Tired as they were, they walked on.
6. 表示也------一樣. She is a doctor, as was her husband.
（二）、 as作關(guān)系代詞,引導(dǎo)定語從句,表示正如,這一點(diǎn).如:
He is very careful, as we all know.
As is well-known, Taiwan belongs to China.
另外,當(dāng)先行詞被the same, such等詞修飾時(shí),常用as來引導(dǎo)定語從句.如:
Such a clever girl as she can learn anything quickly.
I was reading the same book as he bought yesterday.
（三）、as作介詞的用法.
1.表示好像.如:He dressed as a policeman.
2. 表示作為當(dāng)作.如：I found a job as a guide.
3. 當(dāng)某人是某身份時(shí).如：As a child , she was sent to abroad.
4. as引導(dǎo)的介詞短語大多用作狀語,as譯為"作為";少數(shù)情況可引起賓語補(bǔ)足語.如:
As a Party member, I'll take the lead in everything. (狀語)
She works as a model. (狀語)
She has me as one of her best friends.(引起賓語補(bǔ)足語)
（四）、作副詞的用法 1 表示與------等同.如：This dress is twice as expensive as that one. 2 像,如等.如：As before, he remained unmoved.
總之,通過以上的分析,我們對as的詞性和用法有了比較全面的理解和把握,才能在實(shí)際的運(yùn)用中做到心中有數(shù),應(yīng)付自如.限制性定語從句限制所修飾名詞或代詞的意義,一般說來如把從句去掉句子意思就不清楚,甚至失去意義.而非限制性定語從句主句(句子的其他部分)關(guān)系不太緊密,對所修飾名詞或代詞的意思沒有太大影響,把它們拿掉,句子依然很完整,它們可以說是附加上去的東西,而且通常都有逗號把它們和句子的其他部分分開.具體說來,限制性定語從句與非限制性定語從句有以下幾個方面的區(qū)別：

1. 形式不同限定性定語從句主句和從句之間不用逗號隔開,口語中使用時(shí)也不停頓；而非限定性定語從句與主句之間通常2. 作用不同限定性定語從句用于對先行詞的意義進(jìn)行修飾、限制和識別,如果去掉,就會造成句意不完整或概念不清；而非限定性定語從句用于對先行詞起補(bǔ)充說明作用,如果省略,句意仍然清楚、完整： People who take physical exercise live longer.
進(jìn)行體育鍛煉的人活得長些.(若把從句去掉句子就失去意義)
His daughter, who is in Boston now, is coming home next week. 他女兒現(xiàn)在波士頓,下星期回來.(若把從句去句子意義仍然完整)
3. 翻譯不同在翻譯定語從句時(shí),一般把限定性定語從句翻譯在它所修飾的先行詞之前,而把非限定性定語從句與主句分開：He is the man whose car was stolen. 他就是汽車被竊的那個人.
I’ve invited Jim, who lives in the next flat. 我請了吉姆,他就住在隔壁.
我請了吉姆,他就住在隔壁.
4. 含義不同比較：I have a sister who is a doctor. 我有一個當(dāng)醫(yī)生的姐姐.(姐姐不止一個)
I have a sister ,who is a doctor. 我有一個姐姐,她是當(dāng)醫(yī)生的.(只有一個姐姐)
5. 先行詞不同限定性定語從句的先行詞只能是名詞或代詞,而非限定性定語從句的先行詞則可以是名詞或代詞,也可以是短語或句子；另外,當(dāng)先行詞為專有名詞或其他具有獨(dú)一無二性的nt: 2.0">Peter drove too fast, which was dangerous. 彼得開車很快,這是很危險(xiǎn)的.(which指drive too fast)He changed his mind, which made me very angry. 他改變了主意,這使我很生氣.(which指整個主句)Mr. Smith, who is our boss, will leave for Japan LINE-HEIGHT: 18pt; mso-char-indent-count: 2.0">我們的老板史密斯先生下周要去日本.(先行詞為專有名詞,要用非限制性定語從句修飾)
Her father, who has a lot of money, wishes her to study abroad. 她父親很有錢,希望她出國學(xué)習(xí).(先行詞為表獨(dú)一無二意義的普通名詞,要用非限制性定語從句修飾)
6. 關(guān)系詞不同關(guān)系詞that和why可用于限制性定語從句中,通常不用于非限制性定語從句；另外,在限制性定語從句中,關(guān)系詞有時(shí)可以省略,而在非限制性定語從句中關(guān)系詞一律不省略.