When to Use "For" Instead of "Since"?

ESL learners are often unable to decide when to use for instead of since. Take a quick look at these sentences:

  • INCORRECT: Susie has been here since ten days.
  • CORRECT: Susie has been here for ten days.
  • INCORRECT: That house has been empty since three months.
  • CORRECT: That house has been empty for three months. 

Both for and since can be used with a present perfect to talk about duration up to the present, that is, to say how long something lasts. However, for is followed by the period of time; since is followed by the starting point of time.

for + period of time

  • I trust him. I've known him for more than five years.  
  • The Leaning Tower of Pisa has been saved for another 300 years according to its engineers.
  • How long have you been here for? I've been here for six hours. 

since + starting point 

  • Regina's songs have been used in various TV programs and movies since 2005.  
  • They have held rights to the book since the early 1970s
  • I have not seen any of them since that evening.
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