现在完成时since的三种用法是什么？

最佳答案：主要有since+表示过去时间点的词语、since+含有过去含义的时间状语从句、since+一段时间+ago三种用法

【导语】主要有since+表示过去时间点的词语、since+含有过去含义的时间状语从句、since+一段时间+ago三种用法。since有三种词性，作介词，意思是自……以后;何曾，作连词，意思是自……以来;因为，作副词，意思是自……以后;此后;之前，想要学好since的用法，需要结合相关实例展开相关训练。

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：

(1)I've known him since then. 我从那时起就认识他了。

(2)Anna has been ill since January.Anna从1月起一直病着。

(3)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：

(1)I have lived here since I was born. 我从出生起就住在这儿了。

(2)Great changes have taken place since you left. 你走后，变化可大了。

(3)It is two years since I became a postgraduate student. 我考上研究生有两年了。

(4)Great changes have taken place in our city since you left. 你走后我们城市变化可大了。

(5)We haven’t seen each other since we finished our primary school.小学毕业后我们就没有再见面过

(6)It is two years since I became a middle school student. 我上中学有两年了。

(7)He didn’t come last Sunday since he was busy.他因为忙，所以没有来。

(8)Since this method doesn’t work,why not try another?既然这种方法不行，为什么不试用另一种方法呢?

(9)Since you are ill,you don’t need to work here tomorrow.既然你生病，明天就不用来上班了。

(10)I have been in Beijing since you left.自从你离开以来，我一直在北京了。

(11)Where have you been since I last saw you?自上次我和你见面以后，你到哪里去了?

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：

(1)I have been here since five months ago. 我在这儿，已经有五个月了。

(2)I have lived here since five years ago. 五年前我就住在这儿了。

(3)Villa has been a nurse since half a year ago.维拉半年前就当护士了。

(4)He left school two months ago and we haven’t heard about him since.他两个月前离开学校，到现在我们一直没有他的音讯。

(5)He came to Zunyi4 years ago and has lived here (ever) since.他6年前来到遵义，从此便住在这里。