简述in order that ,so as ,so that ,in order to区别及哪个同义哪个?

1. in order that后面接的是目的状语从句,而且该此句的位置不限,可以放在主句之前之后均可.
如：In order that every student might understand it, the teacher explained that passage again and again.
= The teacher explained that passage again and again in order that every student might understand it.
为了使每个学生都明白, 老师反复讲解那一段.
2. so that既可引导目的状语从句,也可以引导结果状语从句.
1）其引导结果状语从句时,so that翻译为“以至于...”,经常可以和so/such...that...转换,且从句只能放在主句之后.
如：He got up late so that he was late for school.
= He got up so late that he was late for school.
2）其引导目的状语从句时,从句只能放在主句之后,此时可以和in order that换用.
如：He got up early so that he could take the first bus. √
= He got up early in order that he could take the first bus. √
但是：So that he could take the first bus, he got up early. ×
3. in order to和so at to均引导目的状语（注意：不是目的状语从句）,即其后为不定式短语.
两者区别在于so as to do sth也不能放于句首,而in order to do sth没有位置限定.
如果目的状语在句尾,则in order to和so as to可以互换.
如： He got up early so as to take the first bus. √
= He got up early in order to take the first bus. √
但是：So as to take the first bus, he got up early. ×