Question

现在完成时since的三种用法

Answer 1

现在完成时since的三种用法如下：

1、since+表示过去时间点的词语/短语

在这里是作介词使用，since+过去一个时间点，如具体的年、月、日期、钟点、last month, half past six等，例如：I've known him since then. 我从那时起就认识他了。

Anna has been ill since January.Anna从1月起一直病着。Sally has done her homework since 9:00a.m.Sally从上午9点就做作业了。

2、since+含有过去含义的时间状语从句

作连词使用，Since用来说明动作起始时间，例如：I have lived here since I was born. 我从出生起就住在这儿了。Great changes have taken place since you left. 你走后，变化可大了。It is two years since I became a postgraduate student. 我考上研究生有两年了。

3、since+一段时间+ago

作副词使用，表示从过去某个时间以来到现在的情形或状态，常与ever连用，例如：I have been here since five months ago. 我在这儿，已经有五个月了。I have lived here since five years ago. 五年前我就住在这儿了。