I found an English site with quizzes which native speakers built.

I was asked to fill in this gap:

How long have you been here _____?



The correct option is "for". I don't know why this answer is correct. I think that an adverb 'since' is a possible answer. First, I want to know why it is incorrect.

since : from a time in the past until a later past time, or until now(Oxford dictionary)

But I don't think that the native speaker made a mistake.

To be a correct answer, The preposition 'for' needs an object. Therefore, there might be an ellipsis in the sentence, and I think an full sentence could be 'how long time have you been here for? Second, Am I right?

  • Incidentally, the bare “How long have you been here?” is better than either of the offered options. May 7, 2022 at 18:44
  • @MichaelLorton I agree with you. Because I have never seen it before.
    – bak1936
    May 8, 2022 at 0:38

3 Answers 3


Since always requires a starting point (a time or a happening).

The question "How long have you been here?" (for isn't strictly necessary) can be answered with a period of time:

I have been here for an hour.

or a starting point:

I have been here since nine o'clock. I have been here since John dropped me off on his way to work.


Both for and since are OK here as the first word in your response. But only for is correct as the last word in the question: *"How long have you been here since?" is a definite error.

The reason for this apparent anomaly is that if you answer the question with, for example, "Since three o'clock", you are not actually answering the question as asked; you are answering the question "Since when have you been here?" This is a perfectly acceptable response, but it is not a syntactic match with the question.

  • In the sentence 'Since when have you been here?' you gave, I have never seen it before. So I had researched for the expression with 'sine when'. There are different opinions or fact. whatever, I don't know exactly, but It is one of the expression in English. Anyway, Thanks! What I have to more think about happened.
    – bak1936
    May 8, 2022 at 0:36
  • It's not a question of opinion, @bak1936. See for instance this, this, or this.
    – TonyK
    May 8, 2022 at 8:55
  • Thanks!! It's really helpful for me. I've just come to know a little about the usage of "since when". Yes, I want to ask you why the answer "since three o'clock" is impossible to the question "How long have you been here since?"If I am given the quiz in the question, I would answer like that, and you said that "it is not a syntactic match with the question." My major isn't English, so I don't know a syntax. Therefore, I failed to understand your statement.
    – bak1936
    May 8, 2022 at 9:41
  • I understand a little it. It is used in doubt, angry and surprising situation like mood. so I think it couldn't match with the question "how long have you been here?." Am I right? If not, I ask you explanation.
    – bak1936
    May 8, 2022 at 10:26
  • I didn't say it was an error. I just meant that it uses a different syntax ("since when") from the question ("for how long"). As I said, it is a perfectly acceptable response.
    – TonyK
    May 8, 2022 at 10:26

Questions in English tend to have a different structure than the corresponding statements. The subject-verb order commonly gets reversed ("Are you here?" instead of "You are here."). Often, the question words (who, what, where, why, when, how) get moved to the front if possible as well.

In this case, the question is "How long have you been here for?", put back into standard sentence structure, would be "You have been here for how long?"

The object of "for" is "how long". There is no ellipsis here.

The version if you use "since" would be *"You have been here since how long?" isn't correct. When referring to time, "since" takes a past event or point in time as an object, not a duration. "Since last week", "Since 4 days ago", "Since I went to the store". Not *"Since two days", or *"Since a semester".

In contrast, "for" can have a duration as an object, but not a past event or point in time. "For a week" is fine. "For a week ago" is fine if you are using a different sense of the word "for", to indicate a purpose ("I bought this book for a week ago", meaning that there was something (contextually understood) that happened a week ago that was the purpose of buying the book).

So it would be fine to ask "You have been here since when?", or in inverted structure, "Since when have you been here?" (Note, the "since" moves with the "when", even though the "for" does not move with "how long".)

  • Can I ask a question? The sentence 'I bought this book for a week ago' which you presented is hard for me to understand. I have never seen the type of sentence before. As I know, there is not only the object of the preposition, but it doesn't seem to show the purpose. but I don't know exactly. Could please show me a supporting evidence for that sentence.
    – bak1936
    May 8, 2022 at 0:26
  • The only answer explaining the difference between for and since gets a downvote? Yes, often people just do not know the grammar. +1 to you.
    – Lambie
    May 8, 2022 at 19:31

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