Since / For

For/since

For is used when specifying the amount of time (how long):

• I've had this watch for more than 5 years.
• I've only known her for a few weeks.
• He's been here for 3 months and still can't speak English.
• She's been smoking for a long time.

Since is used when specifying the starting point:

• I've been n ths buldng since 2014.
• I've only known her since last week.
• He's been here since April and he still can't speak a word of Englsh.
• She's been smoking since she started college.