Things have changed a lot since I wrote to you last time.
She has lived with us since she has come here.
All has changed since he was at home.
I haven’t written to her since she lived in London.
He has never been to see me since I was ill.
Two years have passed since I last smoked.
He has never been to see me since I have been ill.
She has talked little since she has stayed at home.
Since we have owned a car， we have gone camping every year.
She has known me ever since she was a child.
I have live here ever since I was born.
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，含有肯定意味。
It is three years since her husband left her.
It is over sixty years since the People’s Republic of China was established.
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。
It is three years since she stayed here.
How long is it since you were a league member？
6. 在it is+时间+since从句结构中，since从句是现在完成时或过去完成时，均含有否定意味。
It is five years since we have seen her.
It was years since I had seen her.
It’s been a long time since I’ve seen you.
It is four years since I have smoked a cigarette. 我已经4年不抽烟了。
不可说：It is four years since I haven’t smoked a cigarette.
I haven’t been out anywhere since I don’t know how long. 也不知多久了，我哪儿也没去过。
Her mother died when she was a child.
不可说：Her mother has died since she was a child.
She has lived with us since her mother died three years ago.
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，因为在含有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。
It was five years ago that his father died.
It is five years since his father died.