Since is an adverb of time commonly used with the present perfect or present perfect continuous tense.
- I havent seen him since last week.
- It has been raining since morning.
- I have been working since lunchtime.
- I have been waiting for the parcel since Tuesday.
Since can also mean between some time in the past and the present time.
- Last Sunday he went for a drive and has not been seen since.
Since can also be used with past perfect tenses.
- It took me years to get over my break up with Susie. We had been seeing each other since our university days.
Difference between since and for
Since is used with a point of time in the past. For indicates duration.
- It has been raining since morning. (NOT It has been raining since four hours.)
- It has been raining for four hours.
Since as a preposition
When since is used as a preposition, present and past tenses are also possible.
- I havent met her since her marriage.
- Things werent going so well since his fathers death.
- She isnt doing very well since her operation.
Since as a conjunction
Since can also be used as a subordinating conjunction. We can use perfect or past tenses in the since-clause. A since-clause can show cause or time.
- Since he hadn-t paid the bill, his electricity was cut off.
- Since he has apologized, we will not take any further actions against him.
- Since we have no money, we cant buy anything.
- I have admired him since I was a boy.
- I havent seen them since we moved to Mumbai.
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