Here is an citation from a scientific article:

In a well known article, Einstein, Rosen, and Podolsky have given an example of a hypothetical experiment capable of testing [...].

Which article should be used before well-known: a or the?

The article that the authors are refering to is well known to everyone familiar with the subject, it's fair to say that to every reader of the paper. The article is referenced to, if that matters.

As far as I know, we use the definite article to refer to people or objects that are unique. This paper is as unique as it can be. Is it correct to use the indefinite article in this case?

Doesn't the cited sentence mean that there are many well-known papers on the subject and the authors refer to just one of them?

  • Was this article (by Einstein-Rosen-Podolsky) mentioned earlier in the same paper? Apr 10, 2016 at 15:31
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    There are many well-known articles: one of them was written by Einstein et al, and is about this subject. Unless the article has already been mentioned, a is the correct article.
    – JavaLatte
    Apr 10, 2016 at 15:36
  • @CowperKettle, no, this is the first sentence in the paper (after the abstract). JavaLatte, what I meant to say is that there is only one paper writtten by EInstein and other on this subject. Apr 10, 2016 at 15:57
  • @javaLatte, well, the only one I was able to find. Apr 10, 2016 at 16:22
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    Let me say that again: "there are many well-known articles". Full stop. One that comes mind is by two guys named of Crick and Watson. Of these well-known articles, there is an article by Einstein et al, which is about this subject. This article is "a well-known article", one of many.
    – JavaLatte
    Apr 10, 2016 at 16:43

3 Answers 3


The sentence in question correctly uses the indefinite article. The publication written by Einstein, Rosen, and Podolsky may be unique and well-known, but, the way the original sentence is structured, there are not enough clues and pointers to justify using the definite article.

In a well known article, Einstein, Rosen, and Podolsky have given an example of a hypothetical experiment capable of testing...

Even if that particular paper happens to be well-known, the sentence is still referring generically to one paper out of many. It's saying that the trio wrote a paper that provided an example of a hypothetical experiment.

That said, if we use some adjectives to point more specifically to that particular published paper, we could probably rephrase the sentence and invoke the "objects that are unique" rule that you cite.

The well-known Einstein, Rosen, and Podolsky article published in 1935 provided an example of a hypothetical experiment capable of testing...

That sentence would not require the definite article, but it certainly could be used there. Here's perhaps an even better example showing when you might use the definite article to refer to something that is unique, even if it hasn't been previously mentioned in the text:

The theory of relativity was introduced in a 1905 paper published by Albert Einstein.

Conceivably, that sentence could begin with an indefinite article, too, but the resulting sentence would imply that there is more than one theory of relatively (which might be true – however, unless we were trying to draw special attention to that fact, I think the sentence reads better with the definite article, because the theory of relativity is generally well-known and regarded by laypeople as a landmark theory.)

In short, it's not just a matter of whether or not the noun in question is unique, but also how the sentence is structured and what the writer is trying to emphasize.

  • You could restructure the sentence to eliminate the article completely: "Einstein, Rosen, and Podolsky's well-known article published in 1935 gave an example..." (Using "gave" instead of "has given" sidesteps the issue that "E, R, and P" are three people but there is only one article, so neither the singular verb "has given" nor the plural "have given" seem to sound exactly right, whatever the "rules" of grammar say is the correct version.)
    – alephzero
    Apr 10, 2016 at 20:57
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    @alephzero - Sure, you could rewrite the sentence so that no article is required. However, the O.P. seems to be confused about when a definite vs. indefinite article should (or could) be used.
    – J.R.
    Apr 10, 2016 at 23:50

We use the when the listener or reader understands which exact thing we are talking about. Because the reader doesn't know which paper the authors are talking about—the authors haven't talked about it before—they use an indefinite article, a.

Something can be unique or famous, but if the reader does not know which unique thing we are talking about, then we still use a, not the:

  • I met a world-famous actor yesterday.

If the speaker explains exactly which thing, then they can use the:

  • I met the world-famous actor Brad Pitt.
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    Just as a follow-on comment, the authors don't necessarily need to have talked about it first. (That's a common way the definite article gets used, but not the only one.) As a good example, the opening sentence in this Wikipedia article uses the definite article twice and the indefinite article twice: In mathematics, the Pythagorean theorem, also known as Pythagoras' theorem, is a fundamental relation in Euclidean geometry among the three sides of a right triangle.
    – J.R.
    Apr 11, 2016 at 1:11
  • @J.R. No, but if you don't name it or identify it, you need to have talked about it first - see my comments to CowperK above. (Btw, don't assume a backwards relation there. I breathe when I sleep, but I don't necessarily sleep when I breathe. I could have identified it but present it as one of many things) Apr 11, 2016 at 1:13
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    @J.R. Yes. So an important point is that the fact that the thing is unique or well known is not the important factor. A thing may be well-know or unique, but if the speaker's description is not specific enough for the listener to understand which unique thing we are talking about, then they will use s and not the: "I met a world-famous actor yesterday". Apr 11, 2016 at 8:38
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    All true. That said, there are a few things that are so well-known and unique that we almost always use the definite article; e.g.: Two years ago, I went the Louvre, and saw the president of France looking at the Mona Lisa. (When the O.P. refers to a rule that says "we use the definite article to refer to people or objects that are unique," I think those are the kind of things that fall into that category.)
    – J.R.
    Apr 11, 2016 at 14:19
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    @J.R. They may not be the best examples, because arguably they're names. The internet and the universe might be better examples? Apr 11, 2016 at 14:23

You have only to make a small change to make the definite article "felicitous" or appropriate. In doing so, you don't have to name the paper by Einstein, Rosen, and Podolsky, just (as J.R. says) drop enough hints so that the readers can unambiguously identify which paper you are referring to.

In this case, what we're doing is just narrowing down the field of what well known articles we're talking about. The following works:

1 In the well known article by Einstein, Rosen, and Podolsky, the authors have given an example of a hypothetical experiment capable of testing...

Now you are no longer referring to all articles ever written by anybody but only to those written by ER&P.

Interestingly, you could get away with the original sentence by changing a to that:

2 In that well known article, Einstein, Rosen, and Podolsky have given an example of a hypothetical experiment capable of testing...

Here, you are assuming that the readers are familiar with the article you are referring to, and that is sufficient. I will say, however, that the use of that here sounds informal and probably wouldn't actually be used in this context.

For those who might question if that gets the job done, let me posit the following:

3 On that well known day, two airplanes flew into the Twin Towers and a third crashed in Pennsylvania.

Back to your sentence. You could also say:

4 In their well known article, Einstein, Rosen, and Podolsky have given an example of a hypothetical experiment capable of testing...

You've narrowed the field down, again, to well known articles written by PR&G.

As a bonus, I've tried to come up with sentences that have the same structure as the original and would be felicitous with the. It's not been easy.

The following works, for me at least:

5 In the well known Psalm, King David has provided an analogy of the living God as a good shepherd and written: 'The Lord is my shepherd, I shall not want'.

Even if readers come from a nonJudeo-Christian background, they should be able to infer the sentence's meaning even if they can't identify which Psalm it is.

But there's only 150 psalms, and only a few well known ones, whereas there must be millions of academic research papers.

? 6 In the well known tragedy, the Bard, William Shakespeare, used existing sources and rewritten a tale of star crossed lovers, Juliette and Romeo.

This does work if you employ any of the three changes I used for the sentence you ask about. I'm not sure if it works as an opening sentence, in the use of the definite noun phrase we are talking about here, which is to signal to the reader to make an unambiguous identification. (There are other uses the of the definite article, such as to signal a new topic of discussion, to introduce a change in viewpoint, etc. See

The definite article, accessibility, and the construction of discourse referents, David Epstein, 2002. (pdf).)

Now I'm slightly bothered by the fact that if your sentence (using the instead of a) is not felicitous–notice that I have not outright said this–then it seems to conflict with the "Givenness Hierarchy" of Gundel, Hedberg, Zacharski, 1993. See also a 2001 article by the same authors, Definite descriptions and cognitive status in English: why accommodation is unnecessary (pdf.)

Per the "Givenness Hierarchy", if 3 above is felicitous (in any context), then so should the corresponding sentence with the instead of that.

For an easier read and an excellent overview of indefinite and definite articles, see the highly recommended article by Barbara Abbott (pdf.)

As for websites like the one you mention, you can only take those as very rough guidelines. For instance, we can use the indefinite article for unique things too, and also with names, etc.

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