1. For, since and from ‘point forwards’ in time
Ago and before ‘point backwards’ in time.
2. We use for to say how long something lasts
for + period of time
- I once studied the guitar for three years
- That house has been empty for six weeks
- We go away for three weeks every summer.
- My boss will be in Italy for the next ten days.
When we talk about a period of time up to the present, we use for with the present perfect tense (have+ past participle)
- I’ve known her for a long time (NOT I know her…)
A present progressive with for often refers to the future.
- How long are you staying for? (=Until when)
We can leave out for with How long….?
- How long are you staying?
- How long have you been waiting?
3. From and since give the starting point of an action or state: they say when something begins or began.
from/ since + starting point
- I’ll be here from three o’clock onwards.
- I word from nine to five.
- From now on. I’m going to go running every day.
- From his earliest childhood he loved music
- I’ve been waiting since ten o’clock.
- I’ve known her since January.
Since gives the starting point of actions and states that continue up to the present; from gives the starting point of other actions and states
4. For and since can both be used with the present perfect (have + past participle). They are not the same
- I’ve known her for three days.
- I’ve been here for a month.
- I’ve had my car for ages.
since + starting point
- I’ve known her since Tuesday.
- I’ve been here since July.
- I’ve had my car since 1980