【答案】since和for的用法口诀

这两个词都可以和表示时间的词语连用。一般说来，for后接一段时间，用以说明某事一直进行了多长时间，而since后接某一时间(过去的一个时间点)，用以表示某件事开始的时间。

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、ago. 1990 , last month , half past six

I have been here since 1990. 1990起，我一直在这儿。

2.since+ 一段时间+ago

I have been here since five months ago。自从五个月前，我已经在这儿了。

3.since+从句

Changes have taken place since you left. 自从你走后，已经发生了很大的变化。

4.It is +一段时间+since从句

It is two years since I became an English teacher. 我成为英语老师有两年了。

since 和for区别

1.Since+时间点，具体时间

“自从、、、、以来，从、、、以后”用来说明动作起始时间

I have been in Beijing since 2010.

2.For + 时间段，用来说明动作延续时间长度，因此句中的谓语动词，也应该是延续性动词。

I have been in Beijing for one year。

We have learnt English for about three years.

I have been here for 3 days. (对)

I have arrived here for 3 days.（误）