1、As可以引導定語從句.有時可譯爲“正如”.此時，常常是as從句在前，主句在後.
例如：As we can see，he is a Chinese.
2、As 還可引導原因狀語從句，“因爲，由於”
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，隨着”
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.“儘管”.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的單數名詞，倒裝後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.
可變爲 Hard as he works，he never succeed.
