10 Most Common Types of Plagiarism (and How to Avoid Them)

Plagiarism, put simply, is representing someone’s ideas as your own and/or without correct acknowledgment of the original author.

If academic supervisors or peer-reviewed journals find plagiarism in your work, it could lead to rejection or retraction, reporting to your funders, and permanent damage to your academic standing.

In short – it’s not good!

It’s not only wise to avoid it; it’s your ethical duty as a researcher.

The most common types of plagiarism range from flat out copy-pasting from another study to simply misquoting or wrongly citing. Always referencing published text, including your own, and using citations correctly are the key to avoiding plagiarism. But some researchers don’t know every type of plagiarism. That’s dangerous because when discovered, plagiarism reflects poorly on the researcher and their collaborators and funders. Thorough knowledge of all types of plagiarism can save your career.

Plagiarism is clearly defined, but it continues to happen

The Committee on Publication Ethics (COPE) defines plagiarism as:

“When somebody presents the work of others (data, words, or theories) as if they were their own and without proper acknowledgment.”

OK, that’s clear, but plagiarism, both intentional and unintentional, is rampant. It could owe to malice or just ignorance. One study of medical research found that not knowing what qualifies as plagiarism, time constraints, and lack of adequate writing skills were the main causes. These are all easily avoidable.

So, clear up the definitions and avoid trouble. These are 10 of the most common kinds of plagiarism and how you the researcher (or student) can avoid them.

Copy-paste plagiarism

Ctrl-c, ctrl-v (or option-c, option-v) on a Mac. For anyone who works with words, these are two steps for copying and pasting text are a familiar friend. They can also be a criminal accomplice of the lazy researcher.  The most common types of plagiarism start here.

1. Direct plagiarism without citation

This is intentional copy-pasting of others’ work into your own manuscript with no attribution to the original source. This is high school stuff and it should end right there, but it doesn’t.


This may be considered a rare problem in academia, but examples of direct plagiarism are more common than expected. One case study found plagiarism rampant in German medical dissertations. Often, large passages had been copied word-for-word.

This damaged the reputation of the German medical doctorate in other European countries, where a “Dr. med.” is may no longer be recognized as enough for postdoctoral positions or fellowships, owing to low-quality.

From personal experience as a scientific editor, We’ve seen it in studies from all countries. And these were being submitted for peer review. Submitted to a journal!

Plagiarism software like Turnitin will quickly catch it. We, as scientific editors, notice when the English is generally low-level, then there’s suddenly a passage of near-perfect text.

All we editors do is drop it in Google and Google often shows the source, right there. Caught red-handed. Often, it’s self-plagiarism or its methods text, which I’ll get to in a bit. But sometimes, it’s directly copied text.


Even if your study uses very similar methods or yield similar results to another, already published work, you must paraphrase, and cite, these sections. Use proper citation and discuss the similarities and whatever differences may exist.

Give credit where credit is due. You wouldn’t want, or tolerate, someone copy-pasting your published text. If you’re not sure how to paraphrase, ask your supervisor or a colleague. In some cases, an author-guidance company may help you with it. Scize Editing does not do paraphrasing for you, because it’s borderline unethical. Do your best and then send it for an edit. We’re happy to give guidance.

2. Direct plagiarism with citation

In this case, you cite the published work, but the text is directly copy-pasted without quotations. Or you didn’t include the page number(s) of the cited text.


In one case study provided by COPE, a journal reviewer a case where the authors had copied, word-for-word, an entire paragraph in the introduction from another publication as plagiarism. Because the work had been cited in the manuscript, the authors provided a letter of apology and were allowed to address the issue without more repercussions.


Direct copy-pasting is always plagiarism; it doesn’t matter if this is a single sentence or an entire manuscript. Merely citing the source, as in the example above, is not enough; you need to quote the work being cited or rephrase the text.

3. Self-plagiarism

Plagiarizing your own work involves pulling text or entire sections from your own submitted and published work without citing the original.


One of the most frequent forms of self-plagiarism is the recycling of methods sections. In a survey of bioscience methods sections, nearly a third of respondents admitted to completely recycling their own methods sections without citation.

Self-plagiarism can be found with alarming frequency across other parts of publications: a review of 400 medical studies (excluding methods sections) found that more than half of all plagiarism detected was self-plagiarism.


Academic journals and conferences usually hold the copyrights to your published work. Therefore, you need to treat your own published work exactly as you would treat any other publication. Citing and paraphrasing your own work is a simple and efficient way to avoid self-plagiarism.

Whether or not it’s lack of oversight or inadequate education though, we spot it quite often, even more-senior researchers. Granted, methods, especially in STEM sciences such as chemistry, are essentially steps, and there aren’t too many ways to write them. Nor are they necessarily novel enough to warrant citation.

That aside, just copy-pasting them is lazy, and journals that are sticklers about percentages shows in citation software may still hold it against you. Better to reword.

Paraphrased plagiarism

Paraphrasing (the rewording of text in your own words) is a normal part of scientific writing when accompanied by a citation. However, paraphrasing can be plagiarism if the text is changed but no citation(s) is/are provided.

4. Single source plagiarism

Copy-pasting with some work going into changing key words, but without attribution to the original source.

5. Multiple-source plagiarism

This is when you copy-paste from several sources, but with modifications to the text. You may have changed some key words, and you mix multiple sources with similar ideas to generate what looks like new text.

6. Blended plagiarism

In this case, the writing was copy-pasted from published work without citation and used to fill gaps within an otherwise correctly cited and/or original manuscript.


Paraphrased plagiarism comes in many forms. In all cases, the plagiarism is a matter of taking text from a published source and misrepresenting it while not citing it. A very common example is the master’s student who finds a few sources on a topic, copy-pastes them, changes a few words, and presto, new text.

At the student level, in an online class of 20 students, they might get away with it if the text isn’t obviously much more brilliant than the student. But as a researcher, look out. It’s a very bad habit.


Always cite ideas that have been incorporated into your manuscript, even if you have paraphrased the original text. Citing literature reviews or encyclopedia entries is a simple way to both support even common-knowledge claims and to steer you clear of plagiarism charges.

Bad-faith plagiarism

7. Wholesale or partial plagiarism of ideas

This involves your own words, but not your own ideas. You create new text, but it’s a paraphrase of the original source without additional, novel thoughts or ideas.

8. Unoriginal work

This is somewhere between plagiarism and low-quality work. You’ve paraphrased the text and properly cited the source, but the text is close to the structure and content of another published work, which may be your own, or you may have worked on with other co-authors.


Both are deceptive, as well as bad-quality writing. Simply citing references is not enough to avoid plagiarism. A COPE case study shows the dangers of this approach. A journal noticed that an article accepted for publication was highly similar to a conference paper published 5 months before.

The abstract and contents were very close to the other article, but the author lists were completely different. It turned out to be a confused case of partial submissions of research by different parties. Ultimately, the original article was retracted, and the second article was withdrawn.


Obviously, this is tricky. It was hard enough to explain.

What’s clear is that retraction and withdrawal wouldn’t have happened if the authors had been above board in citing the text, not to mention communicating among each other.

All cited text should be paraphrased or quoted correctly to avoid plagiarism. Never copy-paste any published work without proper quoting and referencing.

If you’re referring back to another work, which may or may not be a different collaboration, that’s no different. As COPE recommends, this should generally be taken care of at the institutional level.

If it makes it to peer review, or even worse, to publication and retraction, you’re in quite a bind, and you could’ve avoided it.

Omission-based plagiarism

9. Incidental plagiarism

With incidental plagiarism, you provide citations, but to the wrong source or non-existent/fake sources.


Incidental plagiarism often happens when authors are lazy or careless. It’s also common among students, and it can be tough for instructors to pick up. Especially if you’re working with a niche literature.

For example, you attribute a reference is attributed to findings only partly covered by the cited source. You didn’t read carefully enough and dig deep enough for the right sources or to realize it’s not saying what you say it’s saying.


When citing multiple findings from a source, check the citation and look for the data. Do your reading. If you’re on a research team, make sure your co-authors are accountable and responsible. The lead author should be monitoring this.

Add additional citations as necessary; for example, if the original citation was merely referencing previous findings, rather than was a report on the actual research performed. Another paper’s literature review is a lazy way to go about citation. They did the reading and set out a roadmap, so check their references list and go fetch the original study, read it, and cite it.

10. Accidental plagiarism

This is misquoted or accidentally paraphrased work without a citation. In other words, it’s still plagiarism. This may be the trickiest of all because you don’t know what you don’t know.


One common example of accidental plagiarism involves the adaptation of diagrams, illustrations, or figures. Even if there’s no data (e.g., the diagram illustrates a concept or outlines a model), the original figure needs proper citation.


The simple solution is to be careful and pay attention. Think twice about the 3 a.m. writing sessions and work with a clear head.

Also, when you’re using citation software like EndNote or Mendeley, be careful when sharing files among co-authors, because things can get moved around. Always check references before submission to make sure that nothing’s missing or incorrectly formatted. Cite the original figure when adapting an illustration for your own use.

Conclusion on common types of plagiarism

If English isn’t your first language or if you didn’t receive proper instruction, then some “less-severe” common forms of plagiarism are understandable. Are they forgivable? Depends on who you ask.

We say none of these are forgivable, as they’re avoidable. In university, blame also falls on instructors who don’t stress the importance of plagiarism. Indeed, many instructors are also underinformed or a bit careless (or just tired!).

Fortunately, journals may be forgiving if you’re just missing some page numbers or your methods are a bit too close to similarly worded to those in another study.

But if it’s a simple matter of copy-paste stealing of ideas, there’s really no excuse. Ask your supervisors, your editor, and educate yourself.

The following resources provide more information on definitions of plagiarism and its consequences:

Resources to learn more about avoiding plagiarism

Committee on Publication Ethics (COPE) – COPE sets the standard and is internationally recognized and respected in academic publishing. They also have a rich website with many resources, both for researchers and for peer reviewers and journal editors.

Springer – This provides a good overview of how a major publisher defines and addresses plagiarism.

APA Style Guidelines on Plagiarism and APA Ethics Code – APA is not just for psychology. APA Style is widely applied across the social sciences and even in STEM fields.

A Fresh Look at Self-Plagiarism – Yes, they’re your ideas, but no, you don’t have free reign to copy-paste them after they’re published. Learn more about self-plagiarism here.

Étienne Klein – For some “lighter reading,” here’s the story of a French physicist plagued by plagiarism.

Zhang, Y., & Jia X. Review on the use of CrossCheck for detecting plagiarism in journal articles. Learned Publishing 25: 292-307. doi:10.1087/20120408

Exit mobile version