My understanding is that the toughest standard regarding plagiarism is the "five (consecutive) word" rule, which holds that, if there are five consecutive words identical to someone else's writing, then you are guilty of plagiarism.

This does not apply to, say, proper names like "The Loyal Order of Freemasons", which is considered one word, not five, but what about proverbs or trite expressions such as "My country right or wrong"?

My further understanding is that there are also "looser" standards for determining plagiarism (for example, ten or twenty consecutive "copied" words). When do such standards apply, and when does the five word standard apply?

  • Five consecutive words of original, creative expression - an original creation of the author you're "plagiarizing". If it's not their own original creation, the status of the original comes into play - plagiarizing a plagiarist is plagiarizing the original, but if the original is a part of the public culture, it can't be plagiarized, not once and not twice.
    – SF.
    Apr 3, 2013 at 12:41
  • 3
    My observation, from the perspective of one who was affiliated with a college before I retired, is that "plagiarism rules" are developed by faculty members who cannot stand each other, who object to the opinions of others, and who don't like the students either. So, "Person XYZ plagiarizes" is just a way to avoid saying what they really feel about each other.
    – user23046
    Mar 15, 2017 at 16:33
  • 5
    'five consecutive words' sounds like a good starting point for a piece of software to alert a lecturer to potential plagiarism.
    – evilsoup
    Mar 16, 2017 at 6:59
  • Yes, Five consecutive word should not be a part of others. But some plagiarism checker not following plagiarism rule to detect this.
    – pachi
    Jul 8, 2017 at 8:14
  • Do you have any reference source about this "five words rule"? I have never heard about it, and it would help to know the context it comes from.
    – FraEnrico
    Sep 29, 2017 at 8:24

6 Answers 6


I haven't heard this five-word rule. But I can easily think of many sequences of five words that no one would seriously consider plagiarism.

I think that I will

was the first time that

Britain, France, Germany, and Italy

all men, women, and children

March 1 of this year

turn left at the traffic light (that's six!)

five words in a row

Etc etc.

If some university or whatever institution is classifying as "plagiarism" any use of five words in a row that have ever previously been used anywhere in the world, I think that every student there, not to mention every faculty member, is guilty of plagiarism.

You can't rationally define plagiarism simply in terms of the number of words that are the same. Many short strings of words like those above are the most simple and direct way of expressing a common idea. If you never heard one of those phrasings before, you'd be likely to invent it.

I'm reminded of a TV comedy I saw years ago where a writer of home repair books was accused of plagiarism. And so in court the other writer's lawyer read samples from the two books that were word-for-word identical. Statements like, "Attach the faucet using two screws." At one point the defendant says, "How many ways are there to say, 'Attach the faucet using two screws.' 'Put in the two screws to attach the faucet.' 'Screw in the faucet with two screws.' 'See the two screws? Put 'em in.'"

On the other hand I can think of many short phrases that surely would be plagiarism. Like, "I have nothing to offer but blood, toil, tears, and sweat." "The ultimate question of life, the universe, and everything." "In the beginning, God created the heavens and the earth." "I think, therefore I am." (That's only three words in the original Latin: "Cogito, ergo sum.") If you used one of those strings of words in a way that implied it was original, I think you would be guilty of plagiarism.

  • 1
    I would think those phases would just be an homage
    – Andrey
    Sep 29, 2017 at 15:27
  • @Andrey Rules against plagiarism don't say that you can't copy someone else's words. They say that you can't copy someone else's words without giving proper credit. If you wrote in an academic paper that you had this brilliant new philosophical argument, "I think, therefore I am", that would not only be plagiarism but very lame plagiarism. But you could certainly write, "As Descartes wrote, 'I think, therefore I am.'"
    – Jay
    Sep 29, 2017 at 20:33

You need to remember that plagiarism is not just about words; it can also be about ideas.

So a key point here is that even if you change virtually all of the words, you still need to make sure you cite the source that you are paraphrasing. If you do not cite the source, then it is plagiarism no matter how many words you change.

I have seen students claim to use, say, three or four important books (i.e., by referring to them in footnotes), but then actually take all of the ideas line by line, or paragraph by paragraph (but not word for word), from a website which they do not in any way cite.

This is, unambiguously, plagiarism, even if it is "in their own words". Moreover, there is usually a very clear reason why the student didn't cite that website; they didn't want me to know they had used the website. So it isn't an accidental failure to give credit to the real author, but a deliberate one.

  • 2
    Exactly. And yet somehow the definition of plagiarism has become confused with the configuration of software wholly inadequate for its purported task of detecting plagiarism.
    – user16226
    Mar 15, 2017 at 15:13
  • 1
    You cannot plagiarize an idea. Your example is plagiarism . In that they didn't do anything but use the original writing reworded slightly. But ideas themselves cannot be plagiarized. Many folks have the same idea, heck with that definition most every piece of writing is plagiarized from somewhere else. All murder mysteries are then plagiarized because once someone wrote one all others are just plagiarized.
    – DCook
    Sep 29, 2017 at 18:01
  • @DCook: If you came up with all of Harry Potter on your own, it would not be plagiarism. It's just that you won't, and nobody would believe that you did if what you wrote looked very much like a copy of it. And you certainly can plagiarize an idea, by claiming you came up with it while in reality you got it from someone else.
    – celtschk
    Oct 29, 2019 at 13:53

Plagiarism is an ethical concept, not a legal one, so there is no universal accepted standard. The 'five-consecutive word' is a rule of thumb, not a legal precept. If you are writing for a particular forum, they may have anti-plagiarism guidelines. This is universally true for universities and other educational institutions, you should check your student handbook if this applies to you. These sorts of institutions actually have software comparing student work to other sources, giving details on the points of comparison.

Quotes, properly attributed, are always allowable within reason (you can't "quote" the entire New York Times on your blog without running into legal trouble). Cliches are typically quotes that have lost their attribution through long use (although your 'My country, right or wrong' is part of a longer Stephen Decatur statement). Cliches are generally open for use, but are also boring and lazy writing.

Otherwise, use your best judgment. If you're actually to the point of counting individual words in common, my guess is that your writing is too close to the original. And no fair changing up one or two words or just changing the word order slightly. It's unethical and, possibly more to the point, doesn't work.

  • RE changing one or two words: Yes. If you said "My nation, right or wrong" and presented that as an original quote, I don't think you'd get away with it. But change enough words and at some point you cross the line out of plagiarism. Like I doubt you'd get in trouble for, "I love my nation, even though it has flaws."
    – Jay
    May 15, 2015 at 18:39

Plagiarism is like patent law: You cannot patent something that is not original; you cannot patent "cake" or "bread". Only original mechanisms can be patented: The common screw has been around for so long, you cannot go patent it. You cannot patent the idea of a clock, or coffee cup, or book.

Similarly in plagiarism, you do not plagiarize somebody if you use a sequence of words that obviously (or failing that, you can show) is widely used elsewhere. "My country, right or wrong!" is not plagiarism, it was widely said in the 1870's.

Plagiarism is non-attributed use of original and unique wording. As a rough rule of thumb, the longer the sequence of words involved, when found in some other work, the more probable it becomes the combination was plagiarized. Thus it becomes difficult to find a sequence of, say, 10 words, appearing in works by multiple authors, that were NOT plagiarized. The same may be true (to a lesser extent as many other answers provide examples) for five words, I haven't heard of any five word rule.

I also would not make such a rule in my university, if I sat on a committee deciding such a thing. "Wherefore art thou, Romeo?" is four words and plagiarized. Elementary, dear Watson! is three and plagiarized, although these are both forgivable offenses.

Plagiarism is about stealing original art (word choices and construction) and/or original ideas, to pass them off as your own original construction. As a professor I do not require a reason or have to meet any standard to suspect a student (or other academic) of plagiarism and therefore search for bits I think were probably plagiarized. It is part of my job, as a teacher and academic, to not be so gullible and trusting.

To those that complain I should consider people innocent until proven guilty, that stricture only applies to punishments by those in authority: obviously police must investigate crimes and consider a person guilty in order to bring them to trial and prove it. Punishment should require proof, suspicion and a search for such proof do not require any proof.


Apart from how one would define "plagiarism", there are different rules of thumb for checking the similarity of submitted documents (in my case as a teacher, mostly they are term papers, review papers, chapter summaries etc). Mostly I use the Turnitin's default setting of 1% and sometimes "5 word count". In line with the answers already provided here by other valuable members, the match of five words itself cannot be declared as "plagiarism". Every semester, I try to explain to my students the difference between similarity score and plagiarism. They always ask, Sir, how much plagiarism is allowed? And I always answered, plagiarism, Zero Percent, similarity score, depends on the nature of the assignment. A certain similarity score is not a verdict that student has plagiarized. It is teacher's job to carefully go through similarity report generated by Turnitin to see if student has actually plagiarized.


This is a very interesting conversation. I have not heard of the "five word rule", though I did have an experience in my first year of college where I remember the "16 word rule." I know this because I was called for plagiarism on an assignment in which the task was to write a simple business memo in e-mail format. We were encouraged to work with other students. Another guy in class and I teamed up and wrote a simple memo after reading other examples. Needless to say, they were correct on calling us out! I was roasted on the spot! I was a naive kid in my first month of college and I learned a lesson. In the end, I argued reasonably enough with my Dean to get it taken off of our transcript due to the circumstances and how incredibly obvious it was. I remember the words, "the odds of 16 words in a row is..." that Gail Raikes spoke to me, who was the coincidental author of our college's Cites & Sources book, (the bible on proper report format) which was available conveniently at our bookstore and required by basically every student. But I will never forget the "16 word rule." It was like 1 in a trillion odds, or some other unfathomable number. Either way, 1 in 5 just does not seem like they are considering the numbers that they are actually talking about. Or, it's simply some sort of flag, which would be irrelevant by itself considering every assignment handed in will incidentally fall into this category. NICE topic

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