since的四种用法

 　　1) since +过去一个时间点　(如具体的年、月、日期、钟点、1980, last month, half past six)。

　　I have been here since 1989.

　　2) since +一段时间+ ago

　　I have been here since five months ago.

　　3) since +从句

　　Great changes have taken place since you left.

　　Considerable time has elapsed since we have been here.

　　4) It is +一段时间+ since从句

　　It is two years since I became a postgraduate¹ student.

1 postgraduate   

adj.大学毕业后的，大学研究院的；n.研究生

参考例句：

• I didn't put down that I had postgraduate degree.我没有写上我有硕士学位。
• After college,Mary hopes to do postgraduate work in law school.大学毕业后， 玛丽想在法学院从事研究工作。