Definition of Appendix in a Book or Written Work

When Do You Need to Use One?

The Appendix page of an antique book.
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An appendix is a collection of supplementary materials, usually appearing at the end of a report, academic paper, proposal (such as a bid or a grant), or book. The word appendix comes from the Latin appendere, meaning "hang upon."

An appendix typically includes data and supporting documents used by a writer to develop the written work. Though such information should be of potential use to the reader (not treated as an opportunity for padding), it would disrupt the flow of the argument if it were included in the main body of the text.

Examples of Supporting Materials

Not every report, proposal, or book needs an appendix. However, including one allows you to point to additional information that is relevant but would be out of place in the main body of the text. It can give the reader more depth to the topic, could supply resources for further reading or contact lists, or can provide documentation to make your case for your grant or bid proposal. Appendix information may include tables, figures, charts, letters, memos, detailed technical specs, maps, drawings, diagrams, photos, or other materials. In the case of research papers, supporting materials may include surveys, questionnaires, or schematics and the like that were used to produce the results included in the paper.

"Any truly important information should be incorporated within the proposal's main text," wrote Sharon and Steven Gerson in "Technical Writing: Process and Product." "Valuable data (proof, substantiation, or information that clarifies a point) should appear in the text where it is easily accessible. Information provided within an appendix is buried, simply because of its placement at the end of the report. You don't want to bury key ideas. An appendix is a perfect place to file nonessential data that provides documentation for future reference."

Because of its supplementary nature, it is important that material in an appendix not be left to "speak for itself," wrote Eamon Fulcher in "A Guide to Coursework in Psychology." "This means that you must not put vital information only in an appendix without any indication in the main text that it is there."

An appendix is an ideal place to include information and other data that are simply too long or detailed to incorporate into the main body text. If these materials were used in the work's development, readers may want to reference them to double-check or locate additional information. Including the materials in an appendix is often the most organized way to make them available.

Should You Include an Appendix?

Whether you include an appendix depends on your topic and what will benefit the reader. Will supplemental materials aid the reader's understanding of your topic? Will they provide resources for further reading or exploration? Will they supply additional depth to the data presented in your report, article, book, or proposal? Will the materials provide additional backup for your thesis or message? Do you have items that would be unwieldy to present in a footnote? Make an appendix.

You want the appendix material to be streamlined, relevant to your topic or thesis, and useful to the reader—but it's not a place to put all of your research materials. The citations in the references, bibliography, works cited or endnotes will take care of citing your sources. An appendix is a place for items that help the reader's understanding of your work and research and the topic at hand. If the material is not important enough to refer to in your text, then don't include it in an appendix.

The Difference Between an Appendix and an Addendum

An addendum is new material added to a book or other written work after its first edition has been produced. It could be updated research or additional sources that came to light, further explanation about the book from the author, and the like. 

In a contract, an addendum can change the terms of the contract, such as canceling sections, updating terms or pricing in sections, or whatnot, without the whole contract becoming null and void and needing everyone to sign it anew. The parties to the contract just need to sign the addendum with the noted changes.

Appendix Format Conventions

The way in which you format your appendix depends on the style guide you have chosen to follow for your work. In general, each item referred to in your text (table, figure, chart, or other information) should be included as its own appendix—though if there are many data sets under one grouping, keep them together in their appendix and label each piece appropriately.

If you have more than one appendix, label the appendices "Appendix A," "Appendix B," etc. so that they can be easily cited in the body of the report, and start each on a separate page. Put them in the order that you refer to them in the paper, for ease of use for the reader, and don't forget to note them in the table of contents, if your work has one.

Research papers, including academic and medical studies, usually follow APA style guidelines for the formatting of appendices. They can also follow the Chicago Manual of Style.

  • APA: Center the title, and use upper and lowercase letters. The text of the appendix should be flush left, and you should indent your paragraphs.
  • Chicago: The Chicago style manual also allows for numbered appendices (1, 2, 3, not just A, B, C). As far as location, they appear before any endnotes sections so that any information in the appendices that needs a note can refer to the notes section. If there are many tables in the appendices, though, it might be best to keep the notes with the tables.