Question

where we use for and where we use since ...

Answer 1

HEY MATE HERE IS YOUR ANSWER....


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The use of FOR

We use For when we measure the duration – when we say how long something lasts.

For + a period of time 
To measure a period of time up to the present, we use the present perfect tense and not the present tense.

I have known her for a long time. (Correct) 
I know her for a long time. (Incorrect)I have lived here for ten years. (Correct)
I live here for ten years. (Incorrect)

The present tense with For refers to a period of time that extends into the future.

How long are you here for? (Until when)How long have you been here for? (Since when)

In reality, we can use all verb tenses with For.
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The use of SINCE

Since gives the starting point of actions, events or states. It refers to when things began.

Since + a point in time (in the past), until now.

I've been waiting since 7 o'clock.I have known him since January.

With since we use the present perfect tense or the past perfect tense.

I have been here since 5 o'clock and I am getting tired.I had been working since 5 o'clock and I was getting tired.

Since can also be used in the structure It has been + period of time + since.

It has been two months since I last saw her.It has been three years since the last earthquake.

HOPE IT HELPS YOU....

Answer 2

Here is Ur AnsweR:-

We used For when we measure the duration -- when we say how long something lasts.
ex . They exercise for two hours everyday
He had lived in Delhi for a long time.

Where Since give a starting point of
actions,events or states . it refers to when things began.
ex. I have been waiting since 7'0clock.
I have known him since January.