since的用法

It is +一段时间+since…的句型与It has been +一段时间+since…意思相同，since从句用现在完成时。前者是规范说法，后者是口语说法。

It was+一段时间since从句就用过去完成时。

一、若since引导的状语从句的谓语动词是终止性的过去时

He has studied very hard since he came to our school.自从他来到我们学校，他学习就非常努力。

We have been missing them since they left here自从他们离开这里，我们就一直很想念他们。It has rained a great deal since you left.你走之后下了好多雨。

We have resided in Shanghai since we parted.自从分手以后，我们一直住在上海。

这是最常见的一种用法，此处不再多述。

二、若since引导的状语从句的谓语动词是延续性动词或表示状态的动词的过去式时

I haven’t heard any noise since I slept.这句应译为“我醒后还未听到任何声音”。

John is now with his parents in New Y ork, it is already three years since he was a teacher约翰现在和父母一起住在纽约，他不当教师已经三年了。

It's two years since I smoked我戒烟已经两年了。

How long is it since you lived in Shanghai?你离开（没住在）上海多久了？

It is half a month since he was a League member.他退团（不当团员）半个月了。

It’s been quite some time since I was last in London我离开伦敦已很长时间了。

It has been so long since we were all together. 好久我们没有在一起团聚了。

It is a week since he was in hospital.他出院已有一星期了。

比较：

He has written to me frequently since I was ill.自从我病愈以来，他屡次给我写信。（从句谓语为状态动词）

He has written to me frequently since I fell ill.自从我生病以来，他就屡次给我写信。（从句谓语为终止性动词）

三、若since引导的状语从句的谓语为持续性动词的现在完成时

I haven’t heard from him since he has lived there。这里has lived表示动作的持续性，时间的起点应从：“开始居住”时算起。因此此句可理解为“自从他（开始）住在那儿起，我就一直没收到他的来信”。

Since we have owned a car, we have gone camping every year。自从我们自己有了汽车，我们每年都去野营。

试比较：

Since I’ve been at this school, we have had three headmasters.自从我到这所学校，我们已换了三个校长了。

Since I was at this school, they have had three headmasters.自从我离开这所学校，他们已换了三个校长了。

He has never been to see me since I have been ill. 自从我生病以来，他从未来看过我。

He has never been to see me since I was ill. 自从我病愈以来，他从未来看过我。

四.since与ever连用时，延续性动词的一般过去时充当从句的谓语

She has given me a lot of help ever since she worked in our factory.自她来我们厂工作后，给了我不小的帮助。

值得注意的特例：有个别时候(尤其是用于since I was a child, since we were young之类的表达)，持续性动词或状态动词的一般过去时也可以表示动作或状态持续到现在(多半有ever 修饰)。如：I've known her ever since I was a child. 自孩提时代起我就已经认识她了。We have known each other since we were children. 我们从小认识。I have lived here since I was a child. 我从小就在这里住。She's been playing tennis since she was eight. 她从八岁起就打网球了。Tom hasn't been home since he was a boy. 汤姆从小离家就没回去过。We have lived in England since I was a child. 从我小时起我们就住在英国。