before和ago都能表示在一段時(shí)間以前,但是二者的內(nèi)涵和具體用法有明顯的區(qū)別，以下就是二者的區(qū)別希望能幫助到同學(xué)們學(xué)習(xí)英語(yǔ)

1.ago表示“從現(xiàn)在起的若干時(shí)間以前”，意思是“距今……以前”，需和過(guò)去時(shí)或過(guò)去進(jìn)行時(shí)連用。before泛指“從過(guò)去起的若干時(shí)間以前”，意思是 “距過(guò)去某時(shí)……以前”“與其……（毋寧）”，常和完成時(shí)連用，尤其在間接引語(yǔ)中，如：I visited him three days ago, but he had gone to Shanghai a week before．我三天前去訪問(wèn)他，但他已與那時(shí)的一周前到上海去了。

His parents died ten years ago．他父母十年前都去世了。

He said that his parents had died ten years before．他說(shuō)他父母親十年前都去世了。

I have never been there before．我以前從來(lái)沒(méi)有去過(guò)那里。

2.如果不具體表明多少時(shí)間以前，只用before不用ago，意為“從前、以前”。before仍以副詞的形式置于被修飾語(yǔ)后，常與完成時(shí)候過(guò)去時(shí)連用。如：

Have you seen this film before?

He asked me whether I had been to the Great Wall before．

3.表示在某一點(diǎn)時(shí)間或事件以前時(shí)，只用before不用ago，這種用法是將before當(dāng)作介詞或連詞使用。ago不具有這一功能。如：

They will come back before six o’clock．

It is hoped that this will be finished before the year 1995．希望這件工作將在1995年以前完成

另外，before在句中的含義較多。不少句子中，before雖然引導(dǎo)的也是一個(gè)時(shí)間狀語(yǔ)，但是譯成漢語(yǔ)時(shí)卻不必譯為“在……以前”。

a.如果before引導(dǎo)的從句動(dòng)作發(fā)生得晚或慢，可譯成“……才”。這是主句主語(yǔ)或是名詞、代詞，或用it作形式主語(yǔ)．

He had almost knocked me down before he saw me．他幾乎把我撞倒才看見(jiàn)我。

It will be hours before he arrives．要過(guò)幾個(gè)鐘頭他才回到達(dá)。

You must sow before you can reap．有播種才能有收成。

b.如果強(qiáng)調(diào)從句動(dòng)作發(fā)生之前，主句動(dòng)作已發(fā)生，可譯成“未……就”或“還沒(méi)有……就”。

Before I could get in a word he had measured me．我還沒(méi)有來(lái)得及插話，他就給我量號(hào)了尺寸

Lu Ban built nine pavilions, but before he could finish the tenth, he heard a cock crowing．魯班建了九個(gè)亭子，但他還沒(méi)完成第十個(gè)就聽(tīng)到公雞叫了起來(lái)。

c.有些句子中的before可譯為“先……然后”、“先……再”。

Don’t count the chickens before they are hatched． 不要樂(lè)觀得太早。

Be pupil before you become a teacher．先做學(xué)生，再做先生。

有些句中的before還可譯為“在……內(nèi)”、“趁”、“沒(méi)”。

They arrived before I expected．我沒(méi)想到他們到得那么早。

Study hard before it is too late．趁早努力學(xué)習(xí)。

I had better go now before it is too late．最好我現(xiàn)在就走，免得太遲．

I will be through this book before three days have passed．我要在三天內(nèi)看完這幾本書．

before sb．knew it 一類習(xí)慣說(shuō)法，常譯為“不知不覺(jué)……就”、“還沒(méi)弄清……就”、“不知怎么地……就”。

Time passed quickly and three months went by before Aqiao knew it．時(shí)間飛快的流失，阿巧不知不覺(jué)地在那里度過(guò)了三個(gè)月。

He fell from the tree before he knew it．他不知怎地一下就從樹(shù)上掉了下來(lái)。

4.加強(qiáng)語(yǔ)氣，表示“早已”的意思或使敘述顯得更生動(dòng)，ago也可以用于完成時(shí)。如：

I had thought that he had died at least twenty years ago．我本以為他至少二十年前就去世了。

In fact, I have long time ago known the secret．其實(shí)我早就知道那個(gè)秘密。

5.在表示對(duì)過(guò)去事情猜測(cè)的“情態(tài)動(dòng)詞＋have＋過(guò)去分詞”或“動(dòng)詞的非謂語(yǔ)形式＋have＋過(guò)去分詞”的結(jié)構(gòu)中，ago也可以和完成時(shí)連用。如：

The building is said to have been destroyed in a fire two years ago．據(jù)說(shuō)那棟大樓在兩年前的一場(chǎng)大火中已被燒毀。

The incident must taken place years ago．這是一定發(fā)生在好幾年以前。

You can not have met him a moment ago．剛才你不可能遇見(jiàn)他。

He may have left an hour ago．他可能在一小時(shí)以前就走了。

Having read the article a week ago, I know it very well．一個(gè)星期以前我已讀過(guò)這篇文章，我很熟悉。