連詞
（一）、 as作連詞的用法:
1.作“在-------期間,當----的時候”引導時間狀語從句.注意與when、 while的用法區(qū)別.
①下列情形時,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.如:
As a young man,he was active in sports.
②when作"當……的時候"解,可以指較短的(一點)時間,也可指一段時間.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間或一個過程,強調主句謂語動詞與從句謂語動詞同時發(fā)生.如:Work while you work.Play while you play.
2.As =Since 作"既然"、"由于"解,引導原因狀語從句,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作關系代詞,引導定語從句,表示正如,這一點.如:
He is very careful,as we all know.
As is well-known,Taiwan belongs to China.
另外,當先行詞被the same,such等詞修飾時,常用as來引導定語從句.如:
{{{{Such a clever girl as she can learn anything quickly.
I was reading the same book as he bought yesterday.}}}}