Using since and for

SINCE
(a) I have been here (since eight o'clock, Since Tuesday, Since May, Since 1999, Since January 3, 2001, Since yesterday, Since last month)
Since is followed by the mention of a specific point in time: an hour, a day, a month, a year etc.
Since expresses the idea that something begab at a specific time in the past and continues to the present.
(b) Correct: I have lived here since May
Correct: I have been here since May
(c) Incorrect: I am living here since May
(d) Incorrect: I live here since May
(e) Incorrect: I lived here since May
Incorrect: I was here since May
The present perfect is used in sentences with since:
In (c): The present progressive is NOT used
In (d): The simple present is NOT used
In (e): The simple past is NOT used
Main clause (present perfect)              Since clause (simple padt)
(f) I have lived here                           since I was a child
(g) Ali has met many people             since he came here
Since may also introduce a time clause (i.e, a subject and verb may follow since)
Notice in the examples: The Preent Perfect is used in the maim clause; the simple past is used in the since-clause
FOR
(h) I have been here (For ten minutes, For two hours, For five dsys, For about three weeks, For almost six months, For many years, For a long time)
For is followed by the mention of a lenght of time: two minutes, three hours, four dsys, five weeks etc.
Note: If the noun ends in -s (hours, days, weeks, etc.), use for in the time expression not since.
(i) I have lived here for two years. I moved here two years ago, and I still live here
(j) I lived in Athens for two years. I don' t live in Athens now.
In (i): The use of the present perfect in a sentence with for+a length of time means that the action began in the past and continues to the present.
In (j): The use of the simple past means that the action began and ended in the past.
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