since+一段时间+ago意味着since和for的含义和区别是什么？

"Since +一段时间+ ago"是现在完成时态的一种表达方式。它表示在过去某一时间点之前已经发生了某件事情。与之相反，“Since”后接的动词必须用过去式，如“since I arrived”表示自从我到达以来发生的事情。，，而 "for +一段时间" 是一般过去时态的基本形式，表示过去的动作持续了多久，通常用于描述一种长期或重复的行为。，，"Since +一段时间+ ago"更强调过去发生的事情，而 "for +一段时间" 则更强调过去的动作持续了多长时间。

- 例句：

- He's been in exile in India since 1959, which means he has been away from his home for this long time.

- I have been here for five months, so I have been living in this city for quite some time now.

Since + 一段时间 + ago

- 例句：

- We'll be here for two more days.

- It's been two years since I became an English teacher.

Since + 从 句

- 例句：

- Great changes have taken place since you left.

- Since you left, everything around me has changed dramatically.

It is +一段时间 + since从句

- 例句：

- It's been two years since I became an English teacher.

- It's been six hours since I finished my homework.

For 后面加个时间段

-

- We will stay there for two days.

- We stayed there for four hours after dinner.

英语单词: ago 和 before 的区别

- ago 和 before 的主要区别在于它们所表示的时间范围。

- ago 主要用于过去的时间点，它表达的是某个具体的时间点之前发生的事情。

- before 主要用于过去的某个时间段之前发生的事情，它表达的是某个具体的开始时间之前发生的事情。

需要注意的是，在使用这些词组的时候，需要考虑上下文以及句子的整体意思来确定应该使用哪个词。