一、可以用作介詞
⒈)指時(shí)間上早于，在……之前，如：
She has lived here since before the war.
她從戰(zhàn)前就一直在這兒住。
⒉)指位置在前面，如：
We knelt down before Grandma's grave.
我們在奶奶的墓前跪下。
⒊)指順序或排列在之前，如：
Your name comes before mine on the list.
名單上你的名字在我之前。
⒋)在某人面前，如：
She said it before the witness.
他是當(dāng)著證人的面說的。
二、作為連詞
其基本含義是“在……之前”，又可以根據(jù)不同語境靈活翻譯成“才”、“還沒來得及就……”、“趁……”、“就”等。具體用法如下：
⒈)與情態(tài)動(dòng)詞can/could連用
這時(shí)候從句雖為肯定形式，根據(jù)漢語表達(dá)習(xí)慣譯成“還沒來得及就”，如：
Before I could get in a word，he had measured me.
我還沒來得及插話他就為我量好了尺寸。
Before she could move，she heard a loud noise，which grew to a terribl eroar.
她還沒來得及邁步，就聽見一聲巨響，接著就是可怕的隆隆轟鳴。
⒉)用于肯定句中強(qiáng)調(diào)主句所表達(dá)的時(shí)間，距離長，或花費(fèi)的精力大，譯成“才”
We had sailed four days and four nights before we saw lands.
我們航行了四天四夜才看到陸地。
We waited a long time before the train arrived.
我們等了很長時(shí)間火車才到。
⒊)用于否定句中，強(qiáng)調(diào)主句所表達(dá)的時(shí)間，距離短，或花費(fèi)的精力小，譯成“不到……就”如：
We hadn't run a mile before he felt tired.
我們跑了還不到一英里他就累了。
⒋)主句含有hardly，scarcely等半否定副詞時(shí)可以譯為“剛……就”
這時(shí)候主句應(yīng)用過去完成時(shí)態(tài)，從句用過去時(shí)，還可以用when替代before如：
We had scarcely reached the school before/when the bell rang.
我們剛到學(xué)校鈴聲就響了。
⒌)有時(shí)還有“寧愿”的意思
I'd shoot myself before I apologized to him.我寧死也不向他道歉。
⒍)用于It+be/take+時(shí)間段+before句型
在這一句型中又可以根據(jù)主從句的時(shí)態(tài)分成兩種情況。
若主句是一般時(shí)將來時(shí)態(tài)，從句是一般現(xiàn)在時(shí).若主句是肯定句意思是“要過多長時(shí)間才”;若主句是否定形式翻譯成“用不了多久就”。
It will be two weeks before everything returns to normal.
兩周之后一切才能恢復(fù)正常。
It will be many years before the situation improves.
這種狀況或許要過許多年才能得以改善。
It won't be long before we meet again.用不了多久我們就會(huì)再見面的。
這時(shí)若主句是一般過去時(shí)從句也是一般過去時(shí)。若主句是肯定句翻譯成“多長時(shí)間之后才”，若主句是否定形式翻譯成“沒過多久就”。如：
It was some time before I realized the truth.
過了很長一段時(shí)間我才了解到真相。
It wasn't long before she became a brave solider.
沒過多久她就成了一名勇敢的戰(zhàn)士。
After that it still took seven years before they got married.
他們又過了七年才結(jié)婚。
注意：當(dāng)主句的謂語動(dòng)詞為延續(xù)性動(dòng)詞時(shí)，before與until有時(shí)可以互換。It was an hour before/until the police arrived.
鞏固練習(xí)
⒈(2004天津)It was evening ________ we reached the little town of Winchester.
A.that B.until C.since D.before
2.(2004全國)Several weeks had gone by ________ realized the painting was missing.
A.as B.before C.since D.when
3.(2005廣東)The America Civil War lasted four years ______ the North won in the end.
A.after B.before C.when D.then
4.(2005山東)It was some time _______ we realized the truth.
A.when B.until C.since D.before
5.(2006四川)-Why didn't you tell him about the meeting?
-He rushed out of the classroom _______ I could say a word.
A.before B.until C.when D.after
6.(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
參考答案：D-B-B-D-A-D
