作业帮英语 快 (8 21:15:6)For和Since的区别?
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英语 快 (8 21:15:6)For和Since的区别?
英语 快 (8 21:15:6)
For和Since的区别?
英语 快 (8 21:15:6)For和Since的区别?
在现在（过去）完成时中,两者都是表示“一段时间”.
具体地说,for + 一段时间 ,是能够直接看得出的一段时间,如：for a year,for two months； since在表示“一段时间”时,其本意是指“从过去某一时间点到‘现在’的一段时间,如果作连词使用,其从句中的谓语动词必须具备两个特点：过去时,终止性.
例：He has lived in Beijing for a week.
He has lived in Beijing since a week ago.
He has lived in Beijing since he came here.
前者跟段时间 for a year，
没有时态要求。
后者跟一个时间点 如： since he came back。
通常跟完成时态连用。
前者跟段时间 for a year
后者跟一个时间点 since he came back
Since 用来说明动作起始时间，for用来说明动作延续时间长度。
I have lived here for more than twenty years.
I have lived here since I was born..
My aunt has worked in a clinic since 1949.
Some new oilfi...
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Since 用来说明动作起始时间，for用来说明动作延续时间长度。
I have lived here for more than twenty years.
I have lived here since I was born..
My aunt has worked in a clinic since 1949.
Some new oilfields have been opened up since 1976.
I have known Xiao Li since she was a little girl.
My brother has been in the Youth League for two years.
I have not heard from my uncle for a long time.
注意：并非有for 作为时间状语的句子都用现在完成时。
I worked here for more than twenty years.
(我现在已不在这里工作。)
I have worked here for many years.
(现在我仍在这里工作。)
小窍门： 当现在完成时+一段时间，这一结构中，我们用下面的公式转化，很容易就能排除非延续动词在完成时中的误使。
1) (对) Tom has studied Russian for three years.
= Tom began to study Russian three years ago, and is still studying it now.
2) (错) Harry has got married for six years.
= Harry began to get married six years ago, and is still getting married now.
显然，第二句不对，它应改为 Harry got married six years ago. 或 Harry has been married for six years.
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前者跟时间段 如:for a year，for a month
后者跟一个时间点 ,通常跟完成时态连用。
for加时间段
since加时间点或从句