1.目的状语从句通常用in order that和so that来引导，此时的从句中往往含有情态动词。
It's best to be as short，clear and factual as possible，in order that there may be no misunderstanding.
She said she wanted tea ready at six so that she could be out by eight.
注：so that也可引导结果状语从句，此时后面的从句不存在情态动词；另外，分开写时的 so...that...也表示...结果。
He is so selfish that his teachers and classmates dislike him intensely.
注：目的状语还可以用不定式短语，如in order to do或so as to do来引导（仅是不定式短语，非从句形式）。
They had to take some of his land in order to extend the churchyard.
They were shoving each other out of the way so as to get to the front.
They have tried to limit such imports in order to protect their members jobs.
注：表示否定的目的状语时，以用in order not to do或so as not to do。
Rose trod with care in order not to spread the dirt.
We keep the window shut in order nof to let the flies in.
2. in case that、for fear that和lest都表示以防之意，表示一种否定性的目的。
The foreign teacher spoke slowly in case (that)we misunderstood him.
Sam had consented to take an overcoat in case (that)the wind rose.
The parents crept down the stairs for fear that they should awaken the sleeping baby.
He jotted down his client's address lest he should forget it.