Information considered to be "common knowledge" does not need to be cited (unless you are directly quoting an author). If you are unsure, err on the side of caution and cite the source. "Common knowledge" refers to anything that you expect the readers to already know. An example of general common knowledge is that George Washington was the first U.S. president.
Common knowledge can also be field-specific. For example, a nursing student would not have to cite a basic definition of systolic and diastolic blood pressure, since students and instructors in that field are familiar with the concept already. Here are a few more examples:
Common Knowledge:
- The sky is blue.
Not Common:
- The physics of light refraction explains why the sky appears blue.
Common:
- Ernest Hemingway wrote "The Sun Also Rises".
Not Common:
- Hemingway's life experiences greatly impacted the story, characters and setting in "The Sun Also Rises".
EBOOK: the Complete Guide to Referencing and Avoiding Plagiarism
by
Plagiarism is a tricky topic for many students, but two rules will help guide you:
1. When in doubt, cite it! There are some cases where you may not need to cite (e.g., common knowledge [explained later]), but plagiarism is a "better safe than sorry" situation. If you are not sure whether a source needs to be cited, go ahead and cite it!
2. Ask a librarian! Librarians are the citation/plagiarism experts and are happy to help you. This guide will explain some of the general concepts of plagiarism, but you might still be unsure of what to do in your particular case. Ask a librarian in person, by phone or via the chat box to the right.