Which option is common knowledge and which requires a citation? 

1. Hungary is a landlocked state with many bordering countries, including Slovakia, Ukraine, Romania, Serbia, Croatia, Slovenia, and Austria. It joined the European Union in 2004.
2. China became the largest photo-voltaic manufacturing nation in 2008. It shipped 26,000 MW of PV solar panels, roughly one-third of worldwide total cell shipments.

Did you make your guess? Here is the answer. While both of these statements contain facts, the first one is common knowledge and the second requires a citation. Read on to find out why. 

Common knowledge is defined as “knowledge that most educated people know or can find out easily in an encyclopedia or dictionary” (Yale Poorvu Center for Teaching and Learning, n.d.). Basically, if something is common knowledge, you don’t need to cite the information. However, this concept varies by field and professional level. When in doubt, it is always safer to cite if you aren’t sure if something is common knowledge. 

Key Categories

Common knowledge is divided into key categories, including:

• Birth dates of famous people
• Geographical features
• Historical dates
• Title of a book or painting
• Information an educated person would know

In our example above for "Common Knowledge versus Information Needs a Citation," the Hungary example contains both historic dates and geographic features which are considered common knowledge, or things you could easily look up in an encyclopedia.

Discipline-specific Common Knowledge

Common knowledge also includes basic knowledge that is known by those in a specific discipline or field of study. When writing for that specific field, information that is basic and foundational sometimes does not need to be cited. For example: 

If you were a psychology student, you may not need to cite that Maslow’s hierarchy is one of many behavioral theories. It is an example of common knowledge within a particular field, in this case psychology.

Talk with your professors to learn more about what is considered common knowledge in your class. 

If information is not considered common knowledge, it needs to be cited. Information, work, ideas, or interpretations that are not your own need to be cited. There are some key categories of information that always need to be cited and are not considered common knowledge:

• An image or graphic that is not your own
• Interpretation of facts
• Detailed statistics

In our example above for "Common Knowledge versus Information Needs a Citation," the China example has detailed statistics that would need to be cited (Zhang, 2013, p. 394). Remember, when in doubt, it is always safer to cite!

Yale Poorvu Center for Teaching and Learning. (n.d.). Common knowledge. Retrieved from https://poorvucenter.yale.edu/writing/using-sources/understanding-and-avoiding-plagiarism/common-knowledge.

Zhang, S. and Yongxiu H. "Analysis on the Development and Policy of Solar PV Power in China." Renewable and Sustainable Energy Reviews 21, (2013): 393-401.