高中三年级的日子是苦的，有刚入高中三年级时的迷茫和压抑，有成绩失意时的沉默不语，有晚上奋战到一两点的精神肉体双重重压，也有在清晨凛冽的寒风中上学的艰苦历程。在奋笔疾书中得到常识的快乐，也是一种在巨大重压下看上去茫然无助的痛苦。智学网高中三年级频道为你整理《高中三年级英语要点必学2、since从句的使用方法》期望对你有帮助！
1. Since从句为非延续性动词的过去时或目前完成时，时间的起点应该从从句动作完成时刻算起。
比如：
Things have changed a lot since I wrote to you last time.
自我上次给你写信之后，状况已发生了非常大的变化。
She has lived with us since she has come here.
自从她来到这里，就一直和大家住在一块。
2. Since从句为延续性动词的一般过去时，表示动作或状况的结束。其含义与动词的词义恰好相反，具备否定意味。
比如：
All has changed since he was at home.
自从他离开家将来，这里的所有都变了。
I haven’t written to her since she lived in London.
自从离开伦敦以来，我还没给她写过信。
He has never been to see me since I was ill.
自从我病愈以来，他一直没来看我。
Two years have passed since I last smoked.
我戒烟已经两年了。
但假如since从句是延续性动词的目前完成时，则表示动作由开始延续至说话的时候，具备一定意味。
比如：
He has never been to see me since I have been ill.
自从我生病以来，他一直没来看我。
She has talked little since she has stayed at home.
自从她呆在家将来，就极少讲话。
Since we have owned a car， we have gone camping every year.
自从大家有了汽车后，年年都去野营。
3. 在现代英语中，since从句是延续性动词的一般过去时，有时也可以表示一定意味。此时，多半用ever来加大since的语义。
比如：
She has known me ever since she was a child.
她从小就认识我了。
I have live here ever since I was born.
我生下来就住在这里。
4. 在it is+时间+since从句结构中，since从句是非延续性动词的一般过去时，含有一定意味。
比如：
It is three years since her husband left her.
她老公离开她已经3年了。
It is over sixty years since the People’s Republic of China was established.
中国已经成立60多年了。
5. 在it is+时间+since从句结构中，since从句是延续性动词的一般过去时，含有否定的意味。
比如：
It is three years since she stayed here.
她离开这里已经3年了。
How long is it since you were a league member？
你*有多长时间了？
6. 在it is+时间+since从句结构中，since从句是目前完成时或过去完成时，均含有否定意味。
比如：
It is five years since we have seen her.
大家已经5年没见她了。
It was years since I had seen her.
在那之前，我已经有好久没见到她了。
It’s been a long time since I’ve seen you.
我已经很长时间没见到你了。
另外，①依据英语惯使用方法，since从句不能否定形式出现。
比如：
It is four years since I have smoked a cigarette. 我已经4年不吸烟了。
不可说：It is four years since I haven’t smoked a cigarette.
但因为下句中的since不作“自从”解，所以从句可以用否定形式。
比如：
I haven’t been out anywhere since I don’t know how long.
也不知多长时间了，我什么地方也没去过。
②Since从句一般不与非延续性动词的目前完成时的一定式连用。
比如：
Her mother died when she was a child.
她小时候妈妈就过世了。
不可说：Her mother has died since she was a child.
③Since前不可加表示时间的词汇，但可以与ago连用。
比如：
She has lived with us since her mother died three years ago.
自从她妈妈3年前过世，她就一直和大家住在一块。
不可说：She has lived with us three years since her mother died.
④在It was five years ago since his father died. 一句中的since用错了，由于在含有ago的时间范畴里，已经有了从过去的一个时间点以来的时间，即已有了since的时间范畴，所以再用since是多余的。
改为：
It was five years ago that his father died.
他爸爸5年前过世了。
It is five years since his father died.
他爸爸过世已经5年了。
