ago / before 的用法

'ago' - at a certain time before now

 Ago 与现在相关，从现在往前算有多久，也常与一般过去时连用:

Your mother phoned five minutes ago. Can you phone her back?
I saw her for the first time at film festival in Cannes some twenty years ago.

'before' - any time before now / at a certain time before then

 Before与过去特定之前的时间相关（此时可换用earlier或 previously），也可表示现在之前的不确定的时间；连用的时态可以是 1. 常用现在完成时；2. 一般过去时也可以，但稍少见

Ÿ I know that chap. I've met him somewhere before.
Ÿ Have you been here before? ~ No, I've never been here before. This is my first time.

Ÿ I know that chap. I met him somewhere before.
Ÿ Were you here before? ~ No, I was never here before. This is my first time.  

Ÿ I met him at the AIDS conference in Durban in December 2002 when he told me that he had contracted AIDS four years before. ( = 6 years ago)
Ÿ Last year I went back to my hometown that I had left ten years before and discovered that the house I grew up in was no longer standing. (= left home 11 years ago)
Ÿ Last year I returned to my hometown that I had left ten years ago and discovered that the house I grew up in had been demolished (= left home 10 years ago)

 

'before' – 可用作连词，介词及副词 

注意before是指事件的先后关系，除了用于过去的事件，也可以用于将来的事件；还可以用于现在的一般习惯性事件 

They left the dining table before I had finished my meal. How rude of them!
He knelt down to say his prayers before he got into bed.
I shall read all the reports before I decide what action to take.

I always shave before I take a shower.
You must take off your shoes before you enter the mosque.

 

如果before用作介词，它常用于指时间，不太用于指地点位置（可以用in front of）:  

To stay young and beautiful, try to get to bed before midnight each night. To stay in shape, I try to go for a jog and a swim in the sea every morning before breakfast.
There were so many tall people in front of me that I could see nothing of the procession as it passed by.

【例子】

“Life insurance, before available only to young, healthy persons, can now be obtained for old people and even for pets.”

这里before虽然不是指地点，但却极不自然，可以换用 "previously",  "formerly",  "once",  "at one time"等.

 Ago / before 关系的参考图：

left　　　　　　　visited　　　　　 　NOW
●＿＿＿＿＿＿＿＿＿●＿＿＿＿＿＿＿＿＿●
↑　　　　　　　　　↑＿＿＿＿＿＿＿＿＿|
↑＿＿＿＿＿＿＿＿＿| 　two years AGO
two years BEFORE

I visited my home town two years ago.

Two years ago, I visited my home town, which I had left two years before

Three weeks before I visited Japan, I bought a new suitcase　

 

先考虑这句话正确与否：

We went to the same hotel where we stayed two years before.

 

【案例1】

"I met you two years ago". 转变成间接引语:

 He said that he had met me two years before

似乎天经地义，语法正确，但语义并准确，before还是用ago好，用earlier也行。

不能说ago一定不能与过去完成时连用，如

I knew we had met ten years ago.就是很正常的句子

 

假设你于2004年度假时遇到某人，2006年有来到该地并再次看到了他；现在是2007年， 那么：

He told me we had met three years ago = He told me we met three years earlier in time from now; in other words, in 2004. （现在往前算）
He told me we had met two years before = He told me we had met two years earlier in time from then; in other words, in 2004. （06年再往前算）
这里两句所指的，都是同一个事件.

 

【案例2】

He said he had met me three years ago / before.

本句用ago自然，用before听着会问，“before what”? 如，

He said he had met me three years before I left for Germany.

 

He met me three years ago - from now.
He met me three years before (or earlier). - from a moment that has been established in the context.

用before也不一定要接上完整的细节, 但那样不接，大多情况下给人的感觉会是不完整的

 

Five years ago 是指从说话时往前算的5年

Five years earlier 指从说到的某时候(一般是过去)再往前算5年

& 很多BE speakers把five years ago当成five years earlier用.

Five years before something. 最好说 'five years before I married...' 或 'five years before I moved to India..' （加上了细节）

 

A)I got a message 5 days ago – 这句语义完整. 从现在往前算5天得到信息（假定今天是7号，收到信息是2号。注意实际日常生活中，人们更多地会用I got the message on Sunday这样带具体日子的句子）

B)I got a message 5 days before - before what? 这里需要一个宾语说清楚，哪怕是暗示的也可以. Eg:
I got a message 5 days before Christmas.
I got a message 5 days before my interview.
I spoke to Jim on Friday. I'd got a message 5 days before (I spoke to Jim on Friday)

 

A) 的意思是你在5天前得到消息means you got the message five days before today.
B) 的意思5天前与某个曾提到的日子.
Charlie got a message on the 10th of December.
I got a message five days before (on the 5th of December).

 

【案例3】

以下句子都对

I used to go swimming every day.
I used to go swimming every day when I was a child.
I used to go swimming every day when I lived by the sea.
I used to go swimming every day before I moved to Belfast.

I went swimming every day before I moved to Belfast
I ate chips every day before I went on a diet
I went to the beach every summer before I moved away from the coast

 

I used to play the game before.

这句对，但因为used to, before显得有些多余

 

He came 10 years ago. That would mean in 1999.
He came 10 years before. It is incomplete as it stands without context.
He came 10 years before my 50th birthday. That is complete but you would need to know when my 50th birthday was to know what date he came.
He came 10 years before I did. Also complete, but not helpful, unless you know when I came.
He came 10 years before you did. You would know the date of that one!

 

【案例4】

a)'Penny has been climbing before.' - ' Oh, has she? When was that?'
b)' Penny climbed before'.- 'Oh, Did she? When was that?

两句都对. 第一句表示对爬山的持续性兴趣；第二句表示对Penny来说，爬山是个过去的事.

Before I went to university, I worked / had worked as a carpenter for 5 years.

两者都对 ，也可说
I had been working as a carpenter for 5 years, before I went to the university.

但用一般过去时与过去完成时等，意思是会有些细微差别的

① Before I did X, I did Y - the tense for a simple record of the things one did.
Before I opened the door, I put the key in the lock.
② Before I did X, I had done Y - the tense when one wishes to draw attention to Y, and to lead the listener to an understanding of its relation to X.
Before I opened the door, I had looked carefully into the barn for snipers.
③ Before I did X, I had been doing Y - the tense when one wishes to draw attention to Y, particularly when the fact that one had been doing Y throws strong light on X - it also stresses the continuous element in Y, of course.
Before I took up codebreaking, I had been studying the mathematics of codes for three years.

【案例5】

The house next door had been sold a month before / earlier.

两者都对

这里那两个词均为副词，此时两者的差别很小. Before 常见用法是介词，但 "earlier" 当然没有介词用法，但两句都是长句的简化句:
The house next door had been sold a month before I moved in.
The house next door had been sold a month earlier than the date I moved in.
Earlier  是两个时间的比较， " Before 是两个时间的先后关系.

 

【案例6】

Before I read Freud, I ______dreams were of so much significance.
A) haven't thought
B) wouldn't think
C) didn't think
D) don't think
E) wouldn't have thought   Key C

（I didn't think dreams were of so much significance 要先于 before I read Freud ）

 

【案例7】

Mr. Smith said that John _____ him all about his past three weeks _____?
A. had told...ago
B. had told...before

本题作为一道引语转换题，选B.但问题并不这么简单，句子后面划线的部分写得比较含混，有两个含义：

1. 之前的三个星期的时间"his past three weeks"；

2. 他的过去（的秘密）"his past"

以下按假设句子是2的含义来分析：

(1) Mr. Smith said that John had told him all about his past three weeks ago.
(2) Mr. Smith said that John had told him all about his past three weeks before.
在句子(1), 'three weeks ago' 属于'told'的时间状语，这样句子意思清楚
句子(2)不甚清楚，它可以有（1）的意思，即从现在往前算的时间；但也可以从过去再往前算的时间:

1月1号: John 对Mr. Smith说, 'I have to tell you about my past. When I was 18 I killed a child in a drunk-driving accident.'
1月22号: Mr. Smith对你说, 'John told me about his past, three weeks ago. But I am going to appoint him as a teacher.'
6月30 号: 愤怒的父母了解到John曾在车祸中撞死过人. 他们对质Mr. Smith说， 'When you appointed him as a teacher, did you know about his past?'
Mr Smith回答说, 'Yes, he told (had told) me about his past, three weeks before.'

对后半部分的断句：