Citation allows you to legally reference or use another source in your writing, so it's important to know why/when to include one.
Check out the following links if you have any questions about citation:
English, Religion, Intercultural Studies, Communications
Education, Psychology, Nursing, Social Work
Natural/Physical Sciences, Engineering, Mathematics*
*These disciplines have their own styles for upper-level papers, but use APA for lower-level courses like College Writing.
History, Arts (also can use MLA), Business (also can use APA)
Note: Check your assignment or syllabus paper first to see if it specifies which style to use