I am often confused with the usage of since and from.

I know him from 15 years

I know him since 15 years.

Which one is correct? How would I decide which is the right preposition to use?

2 Answers 2


'Since' and 'From'

'Since' talks about one particular point of time till now.

I have been working since 7 am

'From' in most of the cases talks about the starting point and ending point. Said that, the format could be 'from....to/till/until'

The shop is open from 9 in the morning to 6 in the evening

Quite close is 'since' and 'for'

'Since' and 'For'

Okay, as I said, 'since' talks about a particular point. So, you need to mention "since" which date the thing has been happening.

On the other hand, 'for' is used for a total period of time and you don't need to define a starting point.

The best example I can think of is...

I have been waiting for two hours


I have been waiting since 2 o'clock

In the latter example, you need to define the starting point.

Another example:

I have been living in this house for 10 years
I have been living in this house since 2005

So, in your case, you have known him for the past 15 years OR since 2000.

  • 1
    Not direct to the question; but in the last sentence, you need a past tense to describe the past: "You have known him for the past 15 years," or "You have known him since the year 2000."
    – Evelyn
    Mar 18, 2015 at 6:08
  • 1
    @Evelyn Or, if your knowledge of him is an episode from the past and not continuous, you could say I know him from 15 years ago.
    – choster
    Mar 18, 2015 at 7:05
  • @choster, you're quite right. That usage is almost always followed by specifics of the episode: "I know him from 15 years ago, when we spent a summer working as deckhands on the same fishing trawler."
    – Evelyn
    Mar 18, 2015 at 7:31
  • 1
    still needs 'for the past 15 years' in your last para, or 'for 15 years'. 'past' has to take 'the' Mar 18, 2015 at 9:53
  • @Tetsujin, buddy, you could have done it. :)
    – Maulik V
    Mar 18, 2015 at 9:58

When we use 'since' we generally refer to a particular point of time or a specified time in the past. For example - He has been living here since 1988. She has been awake since dawn / 5'o clock. They have been working here since their youth. So the sentence - " I know him since 15 years " - is wrong. The correct form is - " I know him for 15 years ".

In the same way ' from ' is also used to refer to a particular point of time, and in addition to it, it can also be used to refer to the starting point as well as the ending point. For example - The world cup will start from 14th February. We lived in Oslo from 1988 to 2009.

To refer to a period of time we generally use 'for'. For example - It has been raining in New York for three days.

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