一、用to do sth表目的 用不定式表目的是最簡單也是最常用的方法，它既可以用於句末，也可用於句首，但比較而言，用於句首時，其強調意味較濃。如：
After missing a term through illness he had to work hard to catch up with the others. 他因病一學期未上課，得努力趕上其他同學。
To avoid any delay please phone your order direct. 為免延誤，請直接打電話預訂。
To keep themselves awake they sat on the floor and told each other stories. 為了不至於睡著，他們坐在地板上輪流著講故事。
To avoid back problems， always bend your knees when you lift heavy objects. 為了不使背部受傷，你在扛重東西時，一定要將膝蓋彎曲著。
不定式的否定式為not to do sth，而不是 to not do sth。如：
She had to struggle not to give in to a desire to laugh. 她極力控制自己不要笑出來。
Then there was the mad rush not to be late for school. 然後就是匆忙往學校趕，以免遲到。
I went to France not to study French， but to study architecture. 我去法國不是為了學法語，而是為了學建築。
He claimed he had bought the cigarettes for home consumption， not to sell them. 他聲稱他買菸是為了自家享用，不是為了出售。
二、用so as to do sth表目的
so as to do sth是to do sth的變體，意思是“以便”“為了”“為的是”等。用so as to do sth表示目的時，它通常用於句末。如：
I left a message so as to be sure of contacting her. 我留下了張條子以便與她取得聯繫
The two lovers dropped back so as to be alone. 那對情人落在後面，為的是兩人好單獨在一起。
I always keep fruit in the fridge so as to keep insects off it. 我總是把水果放在冰箱裡，以防蟲子叮咬。
表示目的的so as to do sth有時也可放在句首（但是若so as to do sth是表示結果，則不可放在句首）。如：
So as to show his boss what a careful worker he was， he took extra trouble over the figures. 為了向老闆顯示他是個工作非常細心的人，他在這些數字上費了比平常更多的力氣。
so as to do sth的否定式是so as not to do sth，意思是“為了不……”“以免”。如：
They tiptoed upstairs so as not to wake the baby. 他們踮著腳上樓，以免吵醒孩子。
We left in the daytime so as not to arouse suspicion. 我們在白天離開以免引起懷疑。
I shut the door quietly， so as not to wake the baby. 為了不驚醒寶寶，我輕輕地關上門。
三、用in order to do sth表目的
in order to do sth也是to do sth的變體。用in order to do sth表示目的時，它既可以用於句末，也可用於句首，但比較而言，用於句首時，其強調意味較濃。如：
She lied about her age in order to get the job. 她為了謀得那份工作隱瞞了年齡。
She arrived early in order to get a good seat. 她到得很早，圖的是得個好座位。
Teamwork is required in order to achieve these aims. 完成這些目標需要團隊合作。
In order to get the job you must be able to drive. 要做這項工作你得會開車。
In order to get into a good school， I must study even harder. 為了考入一個好的學校，我必須更加用功。
in order to do sth的否定式是in order not to do sth，意思是“為了不……”“以免”。如：
She slept in a separate room in order not to disturb him. 她在另一房間睡覺，為了不至打擾他。
Please reply at once in order not to lose this opportunity of a lower price. 請立即回覆，以免失去這次低價的機會。
They must have worn gloves in order not to leave any fingerprints. 他們一定戴上了手套，以防留下指紋。
注意，in order to do sth 還有另外一個否定形式，那就是 not in order to do sth，其意為“不是為了……”。如：
Big farmers are moving in， not in order to farm， but in order to speculate with rising land prices. 大農場主正在不斷湧進來，不是為了耕作，而是要利用不斷上漲的地價進行投機。
This expression refers to encounters between ships of hostile nations. One ship might fire a shot at another， not in order to hit it， but to warn it to move. 這個表達源於敵對國船隻在海上相遇時，一方可能向另一方鳴炮，不是為了擊中目標，而是警告其快速離開。
四、用so that表目的
so as to和so that均可表示目的，兩者的區別是，前者引出不定式，後者用以引導目的狀語從句。與用so as to do sth表示目的的情形相似，so that引導的目的狀語從句通常位於主句之後。如：
I will give him a key so that he can get into the house whenever he likes. 我會給他一把鑰匙，好讓他能隨時進來。
I got here early so that we could have a few minutes alone together. 我到這兒早些是為了我們能單獨在一起待幾分鐘。
They wrote the notices in several languages so that foreign tourists could understand them. 他們把通知用幾國文字寫出來，以便讓各國遊客都能看得懂。
有時可省略其中的that。如：
Leave the keys out so (that) I remember to take them with me. 把鑰匙放在外面，好讓我記得帶。
I deliberately didn’t have lunch so (that) I would be hungry tonight. 我有意沒吃午飯，為的就是讓自己今晚能感到餓。
so that 引導的目的狀語從句有時還可置於主句之前（但是，若so that引導的從句是表示結果，則不可放在句首）。如：
So that I shouldn’t worry， he phoned me on arrival. 為了不讓我擔心，他一到就給我打了電話。
So that I shouldn’t forget it， I made a knot in my handkerchief. 為了免得忘記，我將手帕打了一個結。
So that the coming generation can learn the martial arts， he has recently devoted much time to writing books on the subject. 為了下一代能夠學會這些武術，他近來花了許多時間著書立說。
五、用in order that表目的
in order to和in order that均可表示目的，兩者的區別是，前者引出不定式，後者用以引導目的狀語從句。與用in order to do sth表示目的的情形相似，in order that引導的目的狀語從句可以位於主句之前或之後。如：
We arrived early in order that we could get good seats. 我們到得早，以便找到好座位。
These men risk their lives in order that we may live more safely. 這些人甘冒生命危險，為的是讓我們生活更安全。
I bought a new car in order that my wife might learn to drive. 我買了一輛新車，以便我妻子學習駕駛。
In order that you may create such a picture， you have to possess certain artistic weapons. 創作這樣的畫，你得具有某些藝術手段。
六、用in case表目的
in case用於引導目的狀語從句時，意思是“以防”“以免”。如：
He took his umbrella in case it should rain. 他帶上了雨傘，以防下雨。
You’d better take the keys in case I’m out. 你最好帶上鑰匙，以防我不在家。
Listen out for the baby in case she wakes up. 注意聽寶寶的動靜，她醒來好知道。
in case 引導的目的狀語從句有時也可位於主句之前。如：
In case anyone was following me， I made an elaborate detour. 為了防止有人跟蹤我，我特地繞了彎路。
注：也有人認為這樣用的in case 從句為原因狀語從句，意思是“因為怕……”。比較：
I had a snack， just in case there was no time to eat later. 我吃了些點心，以防過會兒沒有時間吃飯。（將in case譯成“以防”，將之視為目的狀語從句）
I had a snack， just in case there was no time to eat later. 我吃了些點心，因為怕過會兒沒有時間吃飯。（將in case譯成“因為怕”，將之視為原因狀語從句）
Here's a contact number， in case there should be a problem. 這是聯繫電話，以防有問題出現。（將in case譯成“以防”，將之視為目的狀語從句）
Here's a contact number， in case there should be a problem. 這是聯繫電話，因為怕有問題出現。（將in case譯成“因為怕”，將之視為原因狀語從句）
七、用for fear (that) 表目的
for fear that 用於引導目的狀語從句時，與 in case 大致同義，意思是“以防”“以免”。如：
He’s working hard for fear (that) he should fail. 他在努力工作唯恐他會失敗。
She finally ran away for fear that he would kill her. 她最後逃走了，因為怕被他殺了。
Scientists reject a total ban for fear it will undermine efforts to stop the spread of malaria. 科學家們反對全面禁止，以免削弱為防止瘧疾擴散所作的努力。
注：與in case一樣，for fear that 引導的從句有時也被理解為原因狀語從句，並將其翻譯為“因為怕……”。比較：
Shut the window for fear that it may rain. 把窗子關上以防下雨。（將for fear that 譯成“以防”，將之視為目的狀語從句）
Shut the window for fear that it may rain. 把窗子關上，因為怕下雨。（將for fear that 譯成“因為怕”，將之視為原因狀語從句）
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