1- For : used with a period of time (can be used with the past, present or future )
we use for to talk about an amount of time or space.it could be seconds, minutes, hours, days, months or even years
ex: - I have been studying English for 10 years .
- I have been trying to reach you for 3 days.
- We have been friends for 2 months.
- I will be staying there for 2 weeks.
- She is staying with us for a week.
- He slept for 20 hours.
2-Since : used to refer to a specific point in time ( it can refer to a point after a specific time or event in the past, a particular point beginning sometime in the past and continuing until the present time)
ex: - I haven't seen her since 2010.
- I haven't slept since yesterday.
- I have been working as an accountant since 2015.
- She hasn't eaten anything since this morning.
- He has been running since 10 am.
