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Lehigh University Libraries - Library Guides

Citations, Summarizing, and Paraphrasing: Common Knowledge

Learn about plagiarism and how to avoid it.

What is common knowledge?

Common knowledge is information that is accepted and known so widely you do not need to cite it:

·         Common sayings or cliches. Examples: Curiosity killed the cat.  Ignorance is bliss. 

·         Facts that can be easily verified. As you are conducting your research on a topic, you will see the same facts repeated over and over.  Example: You are writing a paper on presidential elections, and you want to mention that Ronald Reagan was elected in 1980.  Although you might not have known this fact before your research, you have seen it multiple times and no one ever argues about it. 

·         Facts that you can safely assume your readers know.  Examples: Richmond is the capital of Virginia. The North won the U.S. Civil War.  Fish breathe using gills.

Not all facts are common knowledge. You will still need to cite:

·         Facts that surprise you or your reader.  Example: Michelangelo was shorter than average (1).

·         Facts that include statistics or other numbers. Example: As of June 2009, 42 states have laws that explicitly ban gay marriage, and 6 states have legalized it (2).

·         If you use the exact words of another writer, even if the content within could be considered common knowledge.  Example: "Lincoln’s political career began in 1832, when he ran as a Whig for the Illinois state legislature from the town of New Salem and lost" (3).


Common knowledge can be course-specific.  For example, the number of bones in the leg could be considered common knowledge in an athletic training course.  But if you are using that fact in an English paper, you cannot assume your professor would have that knowledge, and you would need to cite it.

Remember, if you have any questions about whether something is common knowledge, ask your professor for advice.


Works cited:

1. Hughes, Anthony and Caroline Elam. "Michelangelo." Grove Art OnlineOxford Art Online. 15 Jun. 2009<>.

2.  "States Debate Marriage Rights (Research Feature)."  World News Digest.  June 2009.  Facts On File News Services.  15 June 2009  

3. "Lincoln, Abraham." International Encyclopedia of the Social Sciences. Ed. William A. Darity, Jr.. Vol. 4. 2nd ed. Detroit: Macmillan Reference USA, 2008. 450-452. Gale Virtual Reference Library. Gale. RADFORD UNIV. 15 June 2009 , p. 451.