1. “since”是一个介词和副词，指过去某个特定的时间点，在事件、行动或状态的开始时使用。另一方面，“for”意味着一个行为的预期目的，但当涉及到时间时，它显示了某个事物持续的时间量、范围或持续的时间。
2.而“for”表示特定的时间段或持续时间，“since”用于表示特定的时间。
3.当我们用“since”这个词来指一个特定的时间时，主句中使用的动词要么是现在或过去完成时，要么是现在或过去完成连续时态。此外，“since”不能用于将来时。相反，“for”一词可用于所有时态。
for 一段时间 since 过去的时间点 / 一段时间 ago /含有一般过去时的句子用for和since填空
1）I have been in China （ ） 3 years.
2) My grandparents have lived here （） two years ago.
3) We have been friends （） about three years.
4) I have studied English （） 3 years ago.
5) They have lived there （）six years.
6) He has taught in China （） 2006.
7) His English has improved a lot （）he joined the English club.
8) He has learned much English （） he went to England five years ago.
2. 对含有for和since的句子提问用How long 多久
1) I have been in China for （3 years）.（提问）
How long have you been in China?
2) My parents have lived here since （two years） ago.
How long have your parents lived here?
3. since前的句子用现在完成时；since后的句子用一般过去时.
1) l（） (be) in China since I （） (come) here.
2) His oral English （） (improve) since he (join) the English club.
4. 在现在完成时中，瞬间动词不能与含for
和since表示一段的时间状语连用，如果要
连用，瞬间动词要作相应的变化应转换成
延续性动词，变化如下：
leave ______ be away (from)
die ______be dead
buy _______ have
borrow _____ keep
join _______ be in / be a member of
begin _______ be on
come / go / arrive ______ be in
eg：1） My grandfather has died for 30 years. (误)
My grandfather has been dead for 30 years. (正)
My grandfather has been dead since 30 years ago. (正)
2）I have borrowed the book for two weeks. （误）
I have kept the book for two weeks. （正）
I have kept the book since two weeks ago.（误）
3）Lily has bought the skirt for five weeks.（误）
Lily has had the skirt for five weeks. （正）
Lily has had the skirt since five weeks ago.（正）
5. 句型转换
1) I joined the Army two years ago. （同义句）
= I have been in the Army for two years.
= I have been the member of the Army for two years.
= I have been in the Army since two years ago.
= It is two years since I joined the Army.
= Two years has passed since I joined the Army.
2) Her father died three years ago. （同义句）
= Her father has been dead for three years.
= Her father has been dead since three years ago.
= It is three years since her father died.
= Three years has passed since her father died.
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