prep.从…以来； 自从…之后； 自从；
adv.以后，此后； 后来； （距今几年）以前； （从那时候起几年）以前
conj.自从…以来； 自从…的时候起； 既然； 因为
后接某一确定的时间点，主句谓语动词是持续性动词，常与现在完成时态、现在完成进行时态或过去完成时态连用。
例如：
1.He left the village in 1982 and I haven’t seen him since then.1982年他离开这个村子，从那以后我再没见过他。
2.She’s been working in a bank since leaving school.她中学毕业后就一直在一家银行工作。
3.He had spoken to her only once since the party. 自从那次聚会以来，他只跟她说过一次话。
表示从过去以来、以后或到现在的情形或状态，常与现在完成时态连用。
例如：
1.He left home two weeks ago and we haven’t heard from him since. 他两周前离开了家，到现在我们一直没有他的消息。
2.He came to Zhenjiang 6 years ago and has lived here (ever) since.他6年前来到镇江，从此便住在这里。
作为连词，since可引导原因状语从句，表示因为；既然；鉴于：例如：
1.He didn’t come since he was busy.他因为忙，所以没有来。
2.Since this method doesn’t work,let’s try anoter.既然这种方法不行，我们就试用另一种吧。
1.若since引导的状语从句的谓语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”。例如：
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。
2.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动词的过去时时，则从句表示的时间是“从动作或状态结束时算起”。例如：
I haven’t heard any noise since I slept. Sleep 为持续性动词，sleep的动作结束时，即“醒来”时，所以这句应译为“我醒后还未听到任何声音”。
3.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。例如：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”。
句型I：“It is （has been）+时间+since+持续性动词的过去时”，表示“自从……以来到现在已有多久。”例如：
It has been quite some time since I was last in London.我上次离开伦敦至今颇有一段时间了。
句型II：“It was+时间+since+持续性动词的过去完成时”，表示“从……到过去某时间点以来”，例如：It was three years since we had been here.那时我们在这已呆了三年。
(表示时间)从…以来; 自从…之后
I have lived here since January.
自一月份以来, 我一直住在这里。
He had seen her only once since the meeting.
自从那次会议以来, 他只见过她一次。
He's been working in a bank since leaving school.
自从毕业后, 他就一直在一家银行工作。
I have not seen him since then.
从那以后我再也没见过他。
从过去某时间以来[以后, 到现在]
He disappeared many years since.
他多年以前就不知去向。
Her husband died 10 years ago but she has since remarried.
她丈夫于十年前去世, 但她后来又嫁人了。
I've long since forgotten what our quarrel was about.
我早就忘掉我们为什么吵架了。
It was not long since that I returned.
我是在不久前回来的。
He came to London 3 years ago and has lived here ever since.
他三年前来到伦敦, 此后就一直住在这里。
自从(过去某事)以来[以后, 到现在]
Since I left college, I have not seen him.
自从我离开大学以后, 就没有见过他了。
They have never been to see me since I was ill.
自从我生病之后, 他们一直没来看过我。
Since I have owned a bicycle, I have gone to school by it every day.
自从我有了一辆自行车后, 我每天骑车上学。
因为; 既然; 由于
Since it is late I shall go home now.
由于时间晚了, 我现在要回家了。
Since you are so sure of it he'll believe you.
既然你对此这么有把握, 他会相信你的。
1. He has ____ the army for ten years and now is an officer.
A.gone into
B.joined in
C.been in
D.come into
答案：C.(其余三组动词均为瞬间动词，不能和段时间连用。)
2. You don't have to describe her. I _____ her several times.
A.had met
B.have met
C.met
D.meet
答案：B.
I _____ on the door for ten minutes now without an answer.
A.was knocking
B.am knocking
C.knocking
D.have been knocking.
答案:D。 因为该句是说到目前为止已经敲了10分钟了，但没人应答。动作一直持续十分钟。因此完成进行时态是最合适的。
for和since的用法区别
since then的用法
ever since的用法
as soon as的用法