1.As可以引導定語從句.有時可譯為“正如”.此時,常常是as從句在前,主句在后.
例如：As we can see,he is a Chinese.
2.As 還可引導原因狀語從句,“因為,由于”
例如：As he is so lazy,he never cooks by himself.
3.As還可引導時間狀語從句,“當,隨著”
例如：As the weather is colder and colder,the leaves of the tree is less and less.
4.As還可引導方式狀語從句,“按照”
例如：You must do the work as I have told you.
5.As還可引導讓步狀語從句.“盡管”.但是注意,as引導方式狀語從句時從句必須倒裝.而且這種倒裝和一般的倒裝不一樣.as從句的倒裝一般是把從句的表語或作狀語的副詞提到as之前,（如果表語是一個帶有不定冠詞a或an的單數(shù)名詞,倒裝后a或an必須省略).
例如：Though he is a little boy,he knows a lot.如果變成由AS引導,就必須變成：
Little boy as he is,he knows a lot.
Though he works hard,he never succeed.
可變?yōu)?Hard as he works,he never succeed.