since的四種用法

1）since +過去一個(gè)時(shí)間點(diǎn)（如具體的年、月、日期、鐘點(diǎn)、1980, last month, half past six）.

例如：I have been here since 1989. 1989起,我一直在這兒.

2）since +一段時(shí)間+ ago.

例如：I have been here since five months ago. 我在這兒,已經(jīng)有五個(gè)月了.

3）since +從句.

例如：Great changes have taken place since you left. 你走后,變化可真大.

4）It is +一段時(shí)間+ since從句.

例如：It is two years since I became a postgraduate student. 我考上研究生有兩年了.