that的用法歸納總結
下面是小編整理的一些關於介詞since從句的用法的總結， 希望能幫助大家更好地認識since從句，學好英語。
1. Since從句爲非延續性動詞的過去時或現在完成時，時間的起點應該從從句動作完成時刻算起。
例如：
Things have changed a lot since I wrote to you last time.
自我上次給你寫信之後，情況已發生了很大的變化。
She has lived with us since she has come here.
自從她來到這裏，就一直和我們住在一起。
2. Since從句爲延續性動詞的一般過去時，表示動作或狀態的結束。其含義與動詞的詞義恰好相反，具有否定意味。
例如：
All has changed since he was at home.
自從他離開家以後，這裏的一切都變了。
I haven’t written to her since she lived in London.
自從離開倫敦以來，我還沒有給她寫過信。
He has never been to see me since I was ill.
自從我病癒以來，他一直沒有來看我。
Two years have passed since I last smoked.
我戒菸已經兩年了。
但如果since從句是延續性動詞的現在完成時，則表示動作由開始延續至說話的時候，具有肯定意味。
例如：
He has never been to see me since I have been ill.
自從我生病以來，他一直沒有來看我。
She has talked little since she has stayed at home.
自從她呆在家裏以後，就很少講話。
Since we have owned a car， we have gone camping every year.
自從我們有了汽車後，年年都去野營。
3. 在現代英語中，since從句是延續性動詞的一般過去時，有時候也可以表示肯定意味。此時，多半用ever來加強since的語義。
例如：
She has known me ever since she was a child.
她從小就認識我了。
I have live here ever since I was born.
我生下來就住在這裏。
4. 在it is+時間+since從句結構中，since從句是非延續性動詞的一般過去時，含有肯定意味。
例如：
It is three years since her husband left her.
她丈夫離開她已經3年了。
It is over sixty years since the People’s Republic of China was established.
中華人民共和國已經成立60多年了。
5. 在it is+時間+since從句結構中，since從句是延續性動詞的一般過去時，含有否定的意味。
例如：
It is three years since she stayed here.
她離開這裏已經3年了。
How long is it since you were a league member?
你退團有多久了?
6. 在it is+時間+since從句結構中，since從句是現在完成時或過去完成時，均含有否定意味。
例如：
It is five years since we have seen her.
我們已經5年沒有見她了。
It was years since I had seen her.
在那之前，我已經有好久沒有見到她了。
It’s been a long time since I’ve seen you.
我已經很久沒有見到你了。
另外，①根據英語慣用法，since從句不可以否定形式出現。
例如：
It is four years since I have smoked a cigarette. 我已經4年不抽菸了。
不可說：It is four years since I haven’t smoked a cigarette.
但由於下句中的since不作“自從”解，所以從句可以用否定形式。
例如：
I haven’t been out anywhere since I don’t know how long.
也不知多久了，我哪兒也沒去過。
②Since從句通常不與非延續性動詞的現在完成時的肯定式連用。
例如：
Her mother died when she was a child.
她小時候母親就去世了。
不可說：Her mother has died since she was a child.
③Since前不可加表示時間的詞語，但可以與ago連用。
例如：
She has lived with us since her mother died three years ago.
自從她母親3年前去世，她就一直和我們住在一起。
不可說：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用錯了，因爲在含有ago的時間範疇裏，已經有了從過去的一個時間點以來的時間，即已有了since的時間範疇，所以再用since是多餘的。
改爲：
It was five years ago that his father died.
他父親5年前去世了。
It is five years since his father died.
他父親去世已經5年了。
