Since and For
As mentioned in the chapter about
Present Perfect Tense,
since and for are commonly used in combination with
Present Perfect Progressive Tense. Their meaning is slightly different and they should not be mixed up in correct English although the wrong use does not lead to major misunderstandings.
since
The word 'since' is used before a point of time in the past from which a certain even has been lasting till now.
Examples:
I have been working for this company since 2009.
He has been watching TV since three o'clock.
Mum has been reading this book since this morning.
for
The word 'for' is used before a period of time for which an event has been lasting until the present.
Examples: (same as above with the period of time)
I have been working for this company for five years.
He has been watching TV for three hours.
Mum has been reading this book for five hours.
--> Mum has been reading this book the whole day long. (no 'for' needed)