6. FOR, SINCE, AGO
These words are all used to talk about time.
For is used for a period of time that something goes on.
I’ve been working for hours.
I’ll do the job for a year.
I fed his dog for a week.
Since is a specific time in the past.
I haven’t seen you since Monday.
I’ve been working since 10 o’clock.
The pipe has been leaking since yesterday.
ANNE
It’s been a long time since David last called.
Ago refers to a length of time before the present.
I saw you a week ago.
That happened a year ago.
It’s 10 o’clock. You were supposed to be here an hour ago, at 9 o’clock.