前面我們學習了as作為介詞的三大用法，as有“像......、如......”、“作為......”“比如......”三種詞義，在英語中as還作連詞用，有“因為......”、“當......時候”、”按照......“等詞義，在句中引導原因狀語從句，時間狀語從句、方式狀語從句、比較狀語從句、讓步狀語從句、定語從句和伴随狀語從句，這時作為連詞的用法比作為介詞的用法要複雜多了。但隻要我們稍作細心的總結，也能全面掌握的。
1. 引導原因狀語從句：表示“由于......,因為......”常置于句首。
as i’m busy,i cannot play tennis with you all morning.
因為我很忙，不能整個上午和你打網球了。
as we are young,we can’t enter the place of entertainment.
由于我們還小，不能進娛樂場所。
tired as he was, i decided not to disturb him.
因為他累了，我就決定不打擾他了。
2. 引導時間狀語從句,表示“當......時“。
he broke the glass by accident as he brushed the table.
擦桌子時他無意地把杯子弄壞了。
as we walked through the forest ,we heard some strange sounds.
穿過森林時，我們聽到一些奇怪的聲音。
3. 引導方式狀語從句，表示”按照.......“。
the boy can always do his homework as the teacher says.
這男孩總能按照老師的要求做作業。
students must obey the rules as the schools require.
學生必須按照學校要求遵守紀律。
4. 引導比較狀語從句，用”as......as“結構表達。
you can do the job as well as she does.你可以做得跟她一樣好。
jenny didn’t use to sing so beatifully as her mother did.
過去珍妮唱歌沒她媽媽好。
5. 引導讓步狀語從句，表示”雖然......,盡管......“,有轉折的意思。
tired as she was ,she went on doing his homework.
雖然累了，但她仍然繼續做作業。
young as he is, he knows a lot more than other children.
他雖然小，但比其他孩子要懂得很多。
6. 引導定語語從句，置于名詞後。
he is such a good girl as everyone likes.
她是大家都喜歡的好孩子。
mr. li bought the same mobile phoneas i did.李先生買的手機跟我的一樣。
as we expected, he got the first place again .
正如我們所預料的那樣，他又得了第一名。
7. 引導表伴随狀語從句，表示”随着......“.
as time passed, he seemed to get worse.
随着時間的推移，他似乎變得更糟了。
as the environment gets better,more and more birds have appeared in our city.
随着環境的改善，越來越多的鳥出現在我們的城市中。