Difference between Since and For


This post is going to show you a quick and easy way to know when to use since or for.

The words since and for both deal with time. The two words are related to a duration or time period. Both words are prepositions (although since is also an adverb and a conjunction).

For example,

  • I have been teaching English for 10 years.


  • I have been teaching English since 2007.


The way I teach my students on which word to use is in the following manner:

The word for also sounds like the number 4. This reminds me of mathematics.

When you do the math (or calculate the amount of time) for the person then you use FOR.

For example:

  • I have been waiting for 10 minutes.
  • She has lived in the United States for 20 years.
  • He has been raising his hand for an hour.

Do you see how you did the math for the person you were talking to? (You are so nice!).

You calculated the amount of time the person was doing the activity.

When you do the math for the listener, you use FOR.


The word since is completely the opposite. (Thanks a lot!) When you do NOT do the math for the listener, (whether it is because you are not good in math, you are tired or you forgot your calculator) then use since.

I know, the word since is longer than the word for, but that is the price you pay for not doing the math.

Since generally refers to the beginning of some period.

Let’s look at some examples:

  • She has been working out since 2:15pm.
  • They have been studying medicine since 2016.
  • I have been living here since 2013.
  • I haven’t seen Sarah since Friday.

Do you see how I did NOT calculate that number of years or the amount of time in each sentence? So, I need to use the word since. And let your listener do the math!

One last thing about since.

If you use the sentence, “It has been… (years or some time) then you MUST use since when using Present Perfect Verb Tense.

For example,

  • It has been 5 years since I quit smoking.
  • Next month, it will have been 4 years since I have been living in Brazil.
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