【简明语法】11.13 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。