The Difference Between "since" and "for"

The Difference Between "since" and "for"

We use both since and for to say how long something has been happening:
I've been waiting for you since 8 o'clock.
I've been  waiting for you for two hours.
We use "since" when we say the beginning of the period (8 o'clock).
We use "for" when we say the period of time (two hours).

Since	For
8 o'clock          1977 Monday             Christmas 12 may            lunchtime April                 we arrived	two hours       a week ten minutes    five years three days      a longtime six months   ages

She's been working  here since April. (= from April until now)
She's been  working  here for six months. (not  'since six months ')
I haven't seen Tom since Monday . (= from Monday  until now)
I haven't seen Tom  for three day. (not 'since three days ')

We do not use for in expressions with all (all day / all morning / all week / all may life etc.) See the following examples :

1. I've lived here all my life .(not 'for all my life')
2. I've been waiting for you all day. (not 'for all day')

Note the structure How long is it since ...?
A: How long is it since you had a holiday ?
B : it's been two years since  I had a holiday . (= I haven't had a holiday for two years.)
It's ages since Tom visited us. (= He hasn't visited us for ages. )

Exercise

Complete the sentences below with since or for !

1. It's  been  snowing............. I got up this morning.
2. Tom's father has been a doctor ........... 20 years.
3.  Have  you been learning English .............. a long time ?
4.  ........ Christmas, the weather has been quite mild.
5.  Ann has been on holiday ............ five days.
6. That 's a very old bike. I've had it ......... ages.