2015年職稱英語考試已經開始備考，本階段應該多整理一些基礎詞匯和語法。為此，網校特整理了“2015年職稱英語考試語法知識”供您參考，希望對您有幫助！

since的四種用法

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.