1、Since 常见的四种用法1) since +过去一个时间点 (如具体的年、月、日期、钟点、 1980, last month, half past six)。I have been here since 1989.2) since +一段时间+ agoI have been here since five months ago.3) since +从句 Great changes have taken place since you left.Considerable time has elapsed since we have been here. 4) It is +一段时间+ sinc
2、e 从句It is two years since I became a postgraduate student.Since 用法详解：我们都知道 since 的用法主要有两点：一是表示“ 自从以来”，二是表示“既然”之意。但如果只了解词的含义而不了解其用法，在使用时就会造成错误。例如：I have not heard from him since I lived in Shanghai. 不少人会望文生义，将该句理解为：“自从我住在上海以来，就再也没有收到他的信。”而实际上这个句子的含义并非如此，那么正确的理解是什么呢？让我们先来看看 since 作连词引导时间状语从句的用法。一、若 si
3、nce 引导的状语从句的谓语动词是终止性动词的过去时，则从句表示的时间是“从动作开始的那一时刻起”， 这是最常见的一种用法。如：He has studied very hard since he came to our school.自从他来到我们学校，学习就非常努力。二、若 since 引导的状语从句的谓语动词是持续性动词或表示状态的动词的过去时，则从句表示的时间是“从那个持续动作或状态结束时算起”。如：John is now with his parents in New York; it is already three years since he was a teacher.约翰现在
4、和父母一起住在纽约，他不当教师已经三年了。本文开始出现的那个句子就可以译为“自从我离开上海，就再也没有收到他的信。”这种句型常被人们误解，我们再多举几个例子看看：It is half a month since he was a League member. 他退团半个月了。It”s been quite some time since I was in London. 我离开伦敦已很长时间了。比较：He has written to me frequently since I was ill. 自从我病愈以来，他经常给我写信。（从句谓语为状态动词）He has written to me f
5、requently since I fell ill. 自从我生病以来，他就经常给我写信。（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，则表示动作和状态延续到现在（说话时刻），其表示的时间的起点应从动作发生之时算起。如：I haven”t heard from him since he has lived there。自从他住在那儿起，我就一直没收到他的来信。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。Since we have owned a car, we have gone camping every year
6、。 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。由此可见，since 引导的从句中，持续动词的一般过去时和现在完成时所表示的意思恰好相反。换言之，前者以肯定的语法形式反映着否定的逻辑内容，而后者的形式与内容是一致的。It is + 一段时间 + since . 这个句型与 It has been + 一段时间 + since . 意思相同。如：It is ten years / It has been ten years since they last met.自从他们上次碰面之后已经 10 年过去了。
