before的用法是很多的人都比较想要了解的，在众人的心中before的用法是比较难的，我们都非常想要去了解before的用法，但是又谈何容易呢?为了让大家更加快速的了解before的用法，下面我们就和教师一起去看看吧，希望对大家有所帮助。
prep.在……之前;先于，优于;当着……的面;与其……
conj.在……之前;在……以前;比……早些;与其……
adv.先前，从前;在前，在前方
before一词含义广泛，是高考考查的热点词汇之一，但部分考生对该词的用法模糊不清。为了帮助大家掌握，现就对before的用法归纳如下：
一、before用作连词
1. before用作连词时，意思是“在……之前;还没来得及…… 就”。强调主句或从句谓语动词表示的动作发生得过早或过快?例如：
Before she could move, she heard a great noise, which grew to a terrible roar. 她还没来得及动弹，就听见有很响的声音，接着就成了可怕的隆隆轰鸣声。
Before I could say a word, she had stormed out of the room. 不等我说一句话，她就冲出了房间。
Don’t count your chickens before they are hatched. 不要高兴得过早。
I must finish my homework before I watch TV.我必须做完作业才能看电视。
It still took seven years before they finally got married. 过了七年他们才最终得以成婚。
It will be only a few minutes before she comes back. 她过几分钟就会回来。
He announced the ending of the meeting before I could get in a word. 没容得我插上一句话,他就宣布散会了?
Someone called me up in the middle of the night, but they hung up before I could answer the phone.有人半夜给我打电话,但我还未来得及接他就把电话挂断了?
They had talked only a few minutes before they found they were quite different in opinion.他们才谈了几分钟就发现他们的意见很不一致?
注意：before从句若是一个将来的动作，则用一般现在时代替一般将来时，如上句中的comes。
2. 用于It + be + 时间段+ before...句型中，意思是“在……之后才……”。例
如：
It will be five years before I come back.
我五年后才能回来。
It was not long before the enemy was driven out of their country. 不久之后，敌人就被赶走了。
如果主句中用否定式，则表示“不多久……就”。
It won’t be long before they understand each other. 他们不久就会互相了解的。
3. 还有“趁……(还没有)”之意。例如：
They are thinking of buying the house before the prices go up. 他们正在考虑趁房价未涨时把房子买下来。
Do it before you forget it. 趁早动手，以免忘了。
二、before用作介词
before用作介词时, 可以指时间“earlier than在……之前”，也可以指位置“in front of在……之前”。例如：
（1）表示时间，与after相对。如：
August comes before September. 8月份在9月份之前。
There is nothing that has not been bitter before being ripe. 凡事在成熟前，都是有苦味的。
（2）表示顺序，与after 相对。如：
Ladies before gentlemen.女士优先。
（3）表示位置，与behind相对（相当于in front of）。如：
Before Lucy is Lily. 莉莉在露茜的前面。
Don’t put the cart before the horse. 不要本末倒置。
（4）表示“在……面前；与……面对面”。如：
The poor little boy was brought before the headmaster. 那个可怜的小男孩被带到校长面前。
He was brought before the judge. 他被带到法官面前。
（5）表示“宁可……而不愿……”。如：
Death before dishonour. 宁死不辱。
三、before用作副词
（1）before用作副词时，意思是“at an earlier time / in the past以前”。表示“以
前；已经”，单独在句中作状语，句子常用完成时态。如：
I have seen that film before.我以前看过那部电影。
I’ve seen the film Titanic before. 我以前看过《泰坦尼克》这部电影。
I have never seen such beautiful flowers before. 我以前从未见过如此美丽的鲜花。
注意：①区别于ago: ago用在时间段之后，表示某个时间点，句子用一般过去时。如：
I saw that film three years ago.我三年前看了那部电影。
②含有ago 时间状语的直接引语变间接引语时，ago 应变为before。如：
He said to me, “I saw that film three years ago.”
→He told me that he had seen that film three years before.
(2)指空间或位置，表示“在前面”。如：
Look at the page before.看前面一页。
四、
4. 几个需要注意的地方
（1）ever before,单独用作状语，表示“以前”；ever since, 单独用作状语，表示“自从那时以来”；ever after, 单独用作状语，表示“以后；后来”。
（2）before long,单独用作状语，表示“不久以后”，其中long 为名词，后面不接任何成分；可以用于各种时态。例如：
Before long, he went to America. 不久，他就去了美国。
I hope to see you before long. 我希望不久后再见到你。
long before：①单独用作状语，表示“很久以前”，其中before为副词，其后不接任何成分；一般用在过去时或过去完成时的句子里。②表示“在……之前很久”，其中before用作介词或连词，后可接名词、动名词、代词或从句。She said she had read the novel long before. 她说她很久以前就读过这部小说。That happened long before. 那件事发生在很久以前。
（3）when/ while/ if/ unless/ once/ even though 等引导从句时，如果从句主语
和主句的主语相同或为it,并且从句谓语含有be动词，则可以省略从句的主语和be动词部分，形成“when / while / if / unless /once /even though +V-ing或V-ed分词”结构；但是before和after 则不用这一句式，二者后只接动名词或者完整的从句。如：
①When (it is ) translated into English, the word means “newspaper”.
其中it is可省略
②Before being operated on, he took some special medicine.
其中being operated on 为动名词的被动式，being 不可省略。
before可以用作连词,引导时间状语从句?它用法灵活?译法多变,是高考的一个重要考点?现对其用作连词时的用法加以总结,希望对同学们有所帮助?
1.【高考题例】 (加下划线的选项为正确答案)
① (2006四川) —Why didn’t you tell him about the meeting?
—He rushed out of the room______I could say a word.
A. before
B. until
C. when
D. after
② (2003北京) He made a mistake, but then he corrected the situation______it got worse.
A. until
B. when
C. before
D. as
2. before作“……才……”解时,强调从句谓语动词表示的动作发生得太慢或太晚?例如:
The bus driver almost knocked me down before he saw me. 那位公交车司机差一点把我撞倒,他才看到了我?
The fire lasted about four hours before the firefighters were able to control it. 大火持续了大约四个小时,消防队员才把火控制住?
【高考题例】 (加下划线的选项为正确答案)
③ (NMET 2004, Ⅳ) Several weeks had gone by______I realized the painting was missing.
A. as
B. before
C. since
D. when
④ (2005广东) The American Civil War lasted four years______the North won in the end.
A. after
B. when
C. before
D. then
3. before可译为“趁……”?“以免”?“以防”等?例如:
I’ll do it now before I forget it.趁还没有忘,我现在就把这事做了?
We’d better finish the work in time before the boss scolds us.我们最好按时完成这项工作,免得挨老板的骂?
4. before可译为“(宁可……而)不愿”?例如:
He’d die before he apologizes to them.他宁死也不向他们道歉?
I’d give up the plan before I turn to him for help.我宁可放弃计划也不会向他求助?
5. 注意“It + be +一段时间 + before从句”中主句和从句的时态?
该句式中,主句和从句的时态有两种情况:如果主句用一般将来时,则从句用一般现在时,意为“多长时间以后某事即将发生”;如果主句用过去时,从句也用过去时,意为“多长时间后某事才发生”?
【高考题例】 (加下划线的选项为正确答案)
⑤ (2006福建) —How long do you think it will be______China sends a manned spaceship to the moon?
—Perhaps two or three years.
A. when
B. until
C. that
D. before
⑥ (2005山东) It was some time______we realized the truth.
A. when
B. until
C. since
D. before
练一练:
1. (2002上海春) It______long before we______the result of the experiment.
A. will not be; will know
B. is; will know
C. will not be; know
D. is; know
2. (2004福建) Scientists say it may be five or six years ______it is possible to test this medicine on human patients.
A. since
B. after
C. before
D. when
3. (2004天津) It was evening ______we reached the little town of Winchester.
A. that
B. until
C. since
D. before
4. —Why didn’t you help the little boy?
—Oh, sorry. He had struggled to his feet ______I ran over.
A. before
B. after
C. until
D. since
5. Time passed quickly and three weeks went by ______we knew it.
A. before
B. after
C. when
D. till
6. She was such a proud person that she would die ______she would admit she was wrong.
A. rather than
B. until
C. after
D. before
7. We had to sell the vegetables at a low price ______they rotted away.
A. after
B. before
C. when
D. until
8. A dozen ideas were considered ______the chief architect decided on the design of the building.
A. because
B. before
C. whether
D. unless
Key: 1. C2. C3. D4. A5. A6. D7. B8. B