The MLA Handbook (9th ed.) discourages extensive use of footnotes and endnotes. After all, the whole point is to cite your source in the body of the text.
However, sometimes a note may be helpful to provide some information without adding a digression or interrupting the flow of the argument. You can use notes for all kinds of reasons, including explaining what edition of a text you used, listing additional citations when there are a lot of sources, or simply providing more information.
To add a note, place your cursor in the text (typically at the end of a sentence or unit of thought). Then go to the References panel in MS Word and insert either a footnote or endnote. Whichever option you choose, don’t mix and match. The note(s) will show up as a superscript number in your text:
Dietitians are still divided on some key questions. Should the job title be spelled “dietitian” or “dietician”?¹ Is the tomato a fruit or a vegetable?² When does obesity become morbid? However, everyone does agree that forcing children to eat Brussels sprouts is immoral.
Here are the corresponding notes:
¹Like most practitioners (which is also spelled without a “c”), we prefer “dietitian.”
² While the issue appears to be settled in favour of the fruit camp, Olaf B. Ferguson notes that “some Transylvanian critics remain stalwart holdouts” (44). For a fruitful discussion of the issue, see especially Legume and Leek 79-99.
Unless you are publishing online, make sure you indent the first line of each note. Place your cursor before the number and press “Tab.”
Here is another example, for good measure:
³ The same observation is found in subsequent textbooks (e.g., Emerald 101, Luxemburgher 22). Only recently has there been some questioning of the traditional paradigm. See Islander 44 for some probing questions.
When a note primarily adds more references, it is called a bibliographic note, whereas if it consists mostly of added commentary then it is termed a content note.
Notes should use arabic numbering (1, 2, 3, etc.). In addition, text in footnotes is usually in a smaller font (e.g., Times New Roman size 10).
It is up to you (or your instructor) whether you use footnotes or endnotes. If you choose the latter, place them after the text and before the Works Cited. Adding a title such as “Notes” would be a nice touch.
For more information, see chapter 7 of the MLA Handbook (9th ed.).