adv.以后,后来,以前 prep.自从,自...以来 conj.自...以后,自...以来,因为,既然
prep (used with the present or past perfect tense 与现在完成时态或过去完成时态连用) from (a specified time in the past) till a later past time, or till now 从（过去某时间）以来、以後或到现在
*I haven't eaten since breakfast. 我吃了早饭後到现在还什么都没吃呢.
* She's been working in a bank since leaving school. 她中学毕业後就一直在一家银行工作.
* 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.
1 (used with the present perfect, past perfect or simple present tense in the main clause 与主句中的现在完成时态、过去完成时态或一般现在时态连用) from (a specified event in the past) till a later past event, or till now 从（过去某事）以来、以後或到现在
*Where have you been since I last saw you? 自从我上次见到你以後, 你到哪儿去了?
* It was the first time I'd won since I'd learnt to play chess. 自从我学会下国际象棋以来, 这是我第一次赢.
* How long is it since we visited your mother? 自从我们看望你母亲以来到现在有多长时间了?
2 because; as 因为; 既然; 由于
*Since we've no money we can't buy a new car. 因为我们没钱, 没法买新汽车.
3 (idm 习语) ever since =>ever. since adv (used with the present or past perfect tense 与现在完成时态或过去完成时态连用) from a specified time in the past till a later past time, or till now 从过去某时间以来、以後或到现在
*He left home two weeks ago and we haven't heard from him since. 他两星期以前离开了家, 到现在我们一直没有他的消息.
* She moved to London last May and has since got a job on a newspaper. 她去年五月到伦敦, 此後一直在报社工作.
prep, conj, adv
[Language: Old English;Origin: siththan, from sith tham 'since that']
[generally used with a perfect tense in the main clause]
from a particular time or event in the past until the present, or in that period of time
We've been waiting here since two o'clock.
I haven't played rugby since I left university.
She left London ten years ago, and I haven't seen her since.
The factory has been here since the 1970s.
It was exactly five years since her father had died.
Since the end of the war over five thousand prisoners have been released.
He lost his job five years ago, but has since found other work.
I left school in 1995, and since then I've lived in London.
(=all the time since)
We've been friends ever since we were at school together.
She's been terrified of the sound of aircraft ever since the crash.
We came to the UK in 1974 and have lived here ever since.
used to give the reason for something
Since you are unable to answer, perhaps we should ask someone else.
spoken used in questions to show that you are very surprised or angry
Since when have you been interested in my feelings?
if something has long since happened, it happened a long time ago
I've long since forgiven her for what she did.
WORD CHOICE: since, for, during, over
Use since to say that something started at a point in time in the past, and is still continuing : He has been living in Leeds since 1998. | We've known about it since May.
Since is usually followed by a time expression ('last year', 'this morning', '4 o'clock' etc) or by the simple past tense. Use the present perfect or the past perfect in the other clause : I have loved movies since I first went to the cinema. |He had been seriously ill since Christmas.
!! Speakers of British English usually say it is a long time/two weeks etc since ..., and speakers of American English it has been a long time/two weeks etc since ..., but both uses are correct : It's weeks (BrE)/It's been weeks (AmE) since I saw Grandma.
Use for when you state the length of time that something has been happening : We have known each other for ten years (NOT since ten years). | I had been waiting for hours (NOT since hours). |I haven't seen him for ages (NOT since ages).
During and over are used when you state the period of time in which something happens or changes : During her first year at college, she had several boyfriends. | Over the last six months, crime has doubled.