"Since" and "For"

"Since" and "For"

1. since

   • if the starting point is given
     • two o'clock
       • I have been waiting since 4 o'clock.
     • last Friday
       • I haven't been on holiday since last July.
     • 1998
       • Fred and Frida have been learning French since 1998.

2. For

   • if the period of time is given
     • twenty minutes
       • Sue has only been waiting for 20 minutes.
     • two days
       • We have been living here for 2 days.
     • one year
       • Tim and Tina have been learning English for six years.