for - since - ago

For - since - ago are used to talk about time
For is used to say how long an action or situation lasts.



*For is used with the Present Perfect :


- I have been waiting at the bus stop for 10 minutes.

- I have lived in this country for 10 years.



*For can also be used with other tenses :


- Present : I go on holidays for two weeks every year in the summer.

- Past : When I was sixteen, I stayed in London for two months.

- Future : During my trip to California next month, I will be in San Diego for two days.



Since is used to refer to the starting point of actions or situations.

It is generally used with the Present Perfect.


* I have been waiting for the bus since 8 o'clock.

* I live in Tokyo. I have lived in Tokyo since September 2000.


Ago is used to say when past events happened, going back from today towards the past.


* I came to Tokyo three years ago.

* I arrived at the bus stop ten minutes ago.

* I visited New York two years ago.

from: Learn English Today