1） 表示目的；它的否定式是so as not to do。
　　 Tom kept quiet about the accident so as not to lose his job.　
　　　　 湯姆對(duì)事故保持沉默是為了不丟掉他的工作。
　　 Go in quietly so as not to wake the baby.
　　　　 輕點(diǎn)進(jìn)去，別驚醒了嬰兒。

2)　so kind as to ---勞駕
　　 Would you be so kind as to tell me the time?
　　　　 勞駕，現(xiàn)在幾點(diǎn)了。