Citation is your indication that certain material in your work came from another source. It also provides readers with the information necessary to find that source again. Giving credit to the original author by citing sources is the only way to use other people's work without plagiarizing.
The following situations almost always require citation:
Adapted from: Plagiarism.org
A citation serves two main purposes:
A style guide shows you how to format your footnotes, bibliographies, or works cited lists. The style format you use (ALA, MLA, Chicago) depends on which subject you are researching.
Citation style manuals are available online as well as at the Reference Desk. See the Citing Sources page for more detailed information.