A citation is a reference to an outside source of information. It is a way of giving credit to the original author of language or ideas that you are using in your own writing.
Citations appear in the body of text in the form of a parenthetical (or in-text) citation:
... or in a bibliography, list of references, or works cited page:
Citations have several important purposes:
You must provide a citation for any facts, ideas, or data which you take from another source. The only time you do not need to cite is when the fact or idea is 'common knowledge' (see below). You must also provide a citation for any images, graphs, charts, etc. unless you created them yourself.