A citation is:
"A reference providing information about where a particular quotation, text, etc., is to be found; a bibliographical reference."
- Oxford English Dictionary Online, version March 2015
There are many different citation styles which reflect different interests and preferences of disciplines and often publications. If you are unsure which citation style to use, it is best to ask the person you are writing for, such as a professor or journal editor.
You need to cite your sources whenever you:
Cite the source that you used.
In other words, cite only what you have seen. To cite a work that you have not seen or used is dishonest and can perpetuate inaccuracies.
Ideally, you should try to view original sources because other authors may have misrepresented quotes, statistics, ideas or meaning from an original source.
Example: A 2008 article examined the accuracy of citations to a commonly referenced hand surgery study. Of 154 articles that referenced the original study, 63 (41%) had at least one inaccurate reference to this study. The authors concluded: "Care must be taken in referencing biomedical literature, particularly articles that have a potentially profound impact on clinical patient management."
Source: Porrino, J. A., Tan, V., & Daluiski, A. (2008). Misquotation of a commonly referenced hand surgery study. The Journal of Hand Surgery, 33(1), 2–7.
You need to provide enough information for your reader to easily find your sources. The information that you include in a citation depends somewhat on the type of source, e.g. book, book chapter, journal article, or website.
All citations include:
In addition to the information above, citations for BOOKS or BOOK CHAPTERS include:
In addition to the information above, citations for JOURNAL ARTICLES include:
Each has its own benefits. To help you decide which one works best for you, look at the MIT Citation Managers comparison guide.
Can I use this idea from a book or article in my paper?
Yes - just make sure the cite the source properly in your paper. This means a direct quotation or paraphrase and an internal citation. Then include the full citation in the references, bibliography, or works cited page.
Can I use this song on my website? On my video for a course assignment?
Potentially. It depends on the song. A copyrighted song you would have to get permission from the artist or owner. To find openly licensed material that you can use without permission, search Creative Commons.
Can I use this image in my paper?
See the Finding and Using Images guide for more on image citation and copyright.
Can I use this YouTube video for my project?
Depends on the project. If you want to use the video for a course presentation or paper just make sure the credit the creator of the video. If your project is a video project, you will probably need permission from the creator in order to use parts or all of the work. If your project takes the form of a website, you can link the original video or use the embed code from the video (if provided) and the video will be hosted through a site like YouTube, but be embedded in your website.