for or since

UPDATED: NOV 2021

for

= duration or period of time

= 5 days, 2 weeks, many months, several years, most of my life, a long time.)

= usually used with a number (for 10 days, for 2 years)

NOTE:
You can use with All tenses.

NOTE:
Usually answers the question “How long”.

EXAMPLES:

How long were your at the University of Sydney in Australia?
For five years.
How long have you worked in Dallas?
For 2 years.
Fahad has been living in Brisbane for over 3 years.

since

= a specific time in the past (last week, last month, last year, March, 1999)

NOTE:
You can’t use with simple present tense.

“I work with her for a long time.” <= incorrect

NOTE:
You must use Present Prefect or Prefect Continuous

EXAMPLES:

How long have you been here at the UC Berkeley?
Since July of 2019.
Mary has worked in New York since just after 9/11.
Bob has studied Arabic for a year.