since作為介詞后邊接某一確定的時間點，主句謂語動詞是持續(xù)性動詞，常與現(xiàn)在完成時態(tài)、現(xiàn)在完成進(jìn)行時態(tài)或過去完成時態(tài)連用。ever since后面可以不加任何東西，也可以加名詞或者加從句。

since的用法

1、since+過去一個時間點（如具體的年、月、日期、鐘點、1980, last month, half past six）。

I have been here since 1989.

2、since+一段時間+ago

I have been here since five months ago.

3、since+從句

Great changes have taken place since you left.

Considerable time has elapsed since we have been here.

4、It is+一段時間+since從句

It is two years since I became a postgraduate student.

5、用于句型“一段時間+has passed since+時間狀語從句”中，譯作“自從…以來, …（時間）已經(jīng)過去了”。