1）in order to+動詞原形?表示目的，由其引導的目的狀語，置于句首、句尾均可。

I've written it down in order to remember it.

我把它寫下來的目的是記住它

In order to solve the problem, we need to analyze it from different perspectives.

為了解決問題，我們需要從不同的角度進行分析

2）so as to +動詞原形?表示目的，由其引導的目的狀語，只能置于句尾。

He shouted and waved so as to be noticed.

他又喊又揮手,目的是引起別人的注意

3）它們的否定形式分別在to前面加not

I've written it down in order not to forget it.

我把它寫下來目的是不把它忘了

He said nothing so as not to be noticed.

他一聲不吭目的是不被注意到

每日一句：The journey of a thousand miles begins with a single step.千里之行，始于足下