I've just took an English exam and there was a question I must answer using "since".

How long have you known her?

My answer was "I have known her since February". But then I thought what if I wrote like "I know her since..". The question is that if I can use "since" with "simple present tense".

The second thing made me confused is "have known" is present perfect and I think the sentence means you don't know her anymore and how long it took to know her. Is that true? I mean, is that different from "how long do you know her?"? If so, can we say "how long did you know her" instead of saying that sentence with "have you known"?

  • "I've just taken an English exam". Perhaps you were not ready for it. You can look up how to use since and for.
    – Lambie
    Commented Jan 20, 2020 at 18:52

2 Answers 2


1) Your test answer is correct. It matches tense with the question.

2) "I know her since. . ." is not grammatical. The simple present is not used to encompass a period of past time.

3) Present perfect "have known" is exactly the right tense to express something continuing from the past up to the present moment. "Had [verb]" (past perfect) is used for past {event/situation} which {completed/is no longer the case}.

BUT "know" is a special case, semantically unlike other verbs (e.g. support, date, sleep with—see #5.)

4) "How long do you know her?" is not grammatical (see #2.) So it makes no sense to ask whether this means something different.

5) Yes, one might ask "How long did you know her?", but it does NOT mean you don't know her now, BECAUSE once you "know" her, you cannot later not know her. (You could have a falling-out; you might not see her for 20 years, but you still know her.)

So, "How long had you known her" would be asked in reference to a particular moment in the past:

  • How long had you known her when you first kissed her? "For a month".

And "How long did you know her" would be asked in reference to a certain period in the past:

  • How long did you know her before you were engaged? "Eight months."

... but both of the above assume that the "knowing" continues now, and into the future.

  • Thanks for answering. I have two more questions. I didn't understand what the difference between "had you known" and "did you know". Can we also say "How long had you known her before you were engaged?" and "How long did you know her when you first kissed her?" The other question is: Can we make sentences like: "How long have/had you known her since you first kissed her/you were engaged?"?
    – Bora
    Commented May 7, 2015 at 10:39
  • 6) yes you could say "how long had you known her before you were engaged?" with no difference in meaning from "how long did you know her. . . " 7) no, you cannot say "how long did you know her when you first kissed her?" (it likens a span to a moment.) 8) "How long have you known her since..." is grammatically ok, but semantically odd (more likely you would say "how long has it been?") "How long had you known her since . . ." is not grammatical; "since" points forward from the past, but "had" (past perfect) points backwards in the past. Commented May 7, 2015 at 11:11
  • I basically agree with this question but do not agree with the OP's now trying to fish for everything.
    – Lambie
    Commented Jan 20, 2020 at 19:10
  1. Yes, you can use since with Simple Present.
  2. Present Perfect is present Perfect, the whole point of it is that it relates to the present. You still do know her in the present. Otherwise you'd use a past tense and not a present one.
  3. See 2. Yes, you can use the Simple Past, but that would mean that you are talking about something in the past and not the present.
  • Seeing the other answer and some pages on web, are you sure about your 1.?
    – Yohann V.
    Commented May 7, 2015 at 9:14
  • @Yohann: have you read those other pages? Because they specifically quote Swan and CGEL, with the examples "Since last Saturday I can’t stop thinking about you.", "You’re looking much better since your operation", "It’s a long time since the last meeting". COCA has more examples, from CNN and other public networks.
    – ЯegDwight
    Commented May 7, 2015 at 9:35
  • I just read some where it is written you cannot use it, so I'm asking if you are sure about it, you can definitely answering by Yes. (Public networks aren't always corrects)
    – Yohann V.
    Commented May 7, 2015 at 9:40
  • I'm sorry but I would never ever tell an ELLer that "I know her since x" is grammatical in English. It simply does not pass the sniff test. Of course, how AmE speakers speak is a different matter. In any case, those uses you cite are not present simple. One is present progressive and the others are not like the OP's question. Use of modals is a separate case.
    – Lambie
    Commented Jan 20, 2020 at 19:05

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