So I am writing my master's thesis, and am reading a lot of papers. I usually do a lot of 'backtracking' (meaning, read one paper, then look at who they cited and go read those papers).

Doing this, I have found that a lot of authors straight-up copy words and sentences from some of the papers they cite. I don't mean a full paragraph or anything of that sorts, it's almost never more than a sentence, but it does happen a lot.

This is particularly annoying when I read a sentence in one paper and think hmm, that isn't entirely clear and could be expanded upon further, and then I track down the similar concept in another paper to see if there's more info there, but I then find the exact same sentence written there, with no further context provided.

For example, currently I am reading a paper which states

The alternating coefficients of the method may mean that in practice, the theorem does not hold.

I'm not quite sure what they mean by this (why are the coefficients alternating? And why does that impact the validity of the theorem?? Does the theorem not take into account the alternating coefficients???), so I look at a paper they cite that talked about this theorem a bit more, and that paper has the exact same sentence (with no further context).

This makes me think that not only was

  1. the sentence (in the non-original paper) copied straight from the original paper without using quotation marks

but also that

  1. the author of the non-original paper doesn't actually fully understand the meaning of that sentence (just like I don't), and hence, since they don't understand it, they can't write it in their own words, and hence just copied it verbatim.

Am I reading too much into things, or is this behavior common, and if so, what is the proper etiquette concerning what this is acceptable or not?

  • 4
    Aside from your actual question, I'm surprised that anyone would want to copy word-for-word the sentence "The alternating coefficients of the method may mean that in practice, the theorem does not hold"! Unless there is a huge amount of unusual context in which this sentence works well (and I'm not holding my breath regarding this possibility), for a math paper this sentence is venturing into word salad territory -- "alternating coefficients" probably doesn't modify "method, "may mean" is not a definitive existence statement, "in practice" is almost meaningless, etc. Nov 21, 2022 at 15:11

2 Answers 2


As I'm sure you know it isn't correct to just copy things from others. However, there are a couple of additional considerations.

Something is really plagiarism only if it is copied without citation. Then, the author is claiming the work of others as their own. The safest way to avoid this is to use quotes, as you suggest, but certainly to cite.

However, if some of the work you find is old, it is also possible that the standards have changed a bit over time and are now a bit more rigid. Citation and being clear about who originated ideas is the important thing, not, specifically, the punctuation.

But another consideration, especially in fields such as mathematics is that there may be only one way to write some given idea in words. So, in a calculus textbook, for example, the definition of the derivative is nearly identical to every other calculus text on the planet. This sort of thing has actually been discussed in courts, as I understand it.

But for your own work, be as clear as you can be. Cite anything you use and clearly mark what is being quoted using some reasonable typographical convention. Of course you also need to worry about copyright infringement, but that is a different issue. The sloppiness of others shouldn't bleed over into your own work.

The question of copying without understanding is a deeper problem. I won't comment on that.

  • 4
    Quoting a paper without indicating it is a quote, even with a citation, is still very wrong.
    – Bryan Krause
    Feb 15, 2020 at 0:14
  • Maybe we should have a best practice answer for how to cite these "super-common" things, like a common definition that you probably learned from a textbook in class rather than a cutting edge paper.
    – ObscureOwl
    Feb 15, 2020 at 0:22
  • @BryanKrause, yes, of course. But old papers are what they are.
    – Buffy
    Feb 15, 2020 at 1:14

It is definitely not proper etiquette to do that, irrespective of whether it is common or not. I would assume that it is more common in lower quality journals than in higher quality ones. Personally, I have also come across that issue from time to time, and it is definitely a bad (and annoying) practise.

It can probably be considered plagiarism, though it is true that if the original paper is cited, it is less severe. Still, the authors should have explicitly indicated that the sentence that follows is a verbatim quote; and not their own words.

Also, even if quoting properly, generally it is indeed advisable for authors to describe ideas through their own words instead, unless there is a particular reason to quote verbatim.

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