Grammar Tip

Knowing when to use FOR, and when to use SINCE is important. Therefore it is useful to look at a summary of the contrast between FOR and SINCE.

FOR to mention a specific period (or duration) of time.	SINCE to mention the starting point of a period of time (continues to now).
I have been a doctor forfifteen years. (duration = 15 years)	I have been a doctor since 1992. (starting point = 1992)
She has been a mother for six months.	She has been pregnant since her first child was born.
My sister has lived in Moscow for eight months.	My sister has lived in Moscow since the beginning of March.

! It should be remembered that both For and Since have other meanings in English that are not associated with time.