Use an Appendix or Annex in Your Research Paper?

The terms “appendix” and “annex” are commonly confused in research papers. While the use of an appendix is more common, the annex can also be a valuable way of supplementing your research.

Both the appendix and the annex add supporting/supplementary information (SI), like tables and graphs, datasets, or transcriptions. Both are posted online and can be referred to by researchers with a particular interest in your study (especially if they're open access).

The main differences between these two forms of data supplement are context and length. Appendixes are common and are part of the study; you likely used them in theses and dissertations. Annexes deal with much longer and more detailed sets of information, and they're additional to the study's content. Let's take a deeper look at the differences so you'll never them confused.

What is an appendix?

An appendix is, according to Merriem-Webster, “supplementary material usually attached at the end of a piece of writing.” The word comes from the Latin appendere, which means “cause to hang (from something).” It's included in the paper at the end, usually after the references or bibliography.

Appendixes/Appendices can be seen as materials that supplement rather than complement the research. Read only by those with a specific interest.

Basics of an appendix

The following are generally true of an appendix.

• Included at the end of the manuscript.
• Written by one more of the paper's researchers. Exceptions are items like letters granting ethical clearance for the research or details of the research tools used (see the example later).
• Ties into the research directly; gives greater detail than the main body of the manuscript.
• Not too long. Of course, that's subjective, but generally speaking, it's a page or two rather than dozens of pages, or more.

What to put in an appendix

Some examples of an appendix are:

• Figures and tables
• Maps
• Photographs
• Raw data (tables, plots, images)
• Questionnaires and interview questions (especially in qualitative research)
• Ethics approvals such as from the IRB
• Correspondences, such as letters or emails

Most research published as a journal article, and particularly as a thesis, will contain appendices rather than annexes.

This paper (PDF link) includes an appendix that details the instruments used in the research. Each test was used in the study, and the author felt the details were important enough to detail in the appendix, too much information to be presented in the main paper.

This chemistry article also presents supplementary data in the appendix. As it's too lengthy to put in print, a downloadable Word file is available. However, it's only data rather than an article or other full and standalone materials, which is likely why it was made into an appendix rather than an annex.

What is an annex?

Merriam-Webster defines an annex as “an added stipulation or statement.” In the context of research, both academic and commercial, annexes are usually separate additions to the research output and are submitted as separate documents.

Annex comes from the French annexer, which means “to join or attach.” Simply put, an annex comes along with (joining or attached to) a research paper. An example might be a UN report relevant to a manuscript, and that will be added as a supporting document, backing up the research findings. Annexes are used for materials that complement the research.

Basics of an annex

The following are generally true of an appendix.

• Attached to the research paper as a separate item.
• Often (but not always) produced by someone outside the research team. If, for example, one of the researchers produced a white paper for the government on the research domain and this might complement the research, this could be an annex.
• Can be many pages long.
• Supports or informs the research that has been done; complements it.
• Is not part of the research output presented in the manuscript's body text.

What to put in an annex

Some examples of an annex are...

• Documents mentioned in the manuscript or that may support the manuscript
• News articles
• Lab reports
• Interviews of people mentioned in the manuscript.
• Data from other studies

Almost always, annexes are added to papers that exceed normal journal article lengths. They're supporting materials to lengthy research output, like those often funded by corporate or government funding.

This World Health Organization guidance paper on HIV/AIDS is itself 21 pages long but comes with separate downloadable annexes. The paper details the findings stemming from the research and describes the processes for the trials. On page 5, the paper notes that the annexes are included to give greater details on the clinical trials mentioned in the paper. In this sense, the annexes are for readers who want greater detail.

The paper reviews the trials done in the annex, but because the trials were not part of the research and was done by others, it was added as an annex.

Should you use an appendix or an annex?

Short answer: you should probably use an appendix. That's because they're much more common. Appendices are placed at the end of a document, while annexes are, technically, separate from it. The former is part of the paper, but the latter is not.

Annexes are often long documents, running even to hundreds of pages. Most often, someone an annex's author is someone who's not part of the research team. Appendices, however, are often by a paper's author(s) and are usually not more than a few pages each (though, in the case of datasets, they technically can be quite long).

Annexes are used to verify the research and provide additional, relevant information. They are documents from credible and relevant sources. They offer further insight into the research topic.

Normally, you'll be using appendices, and that's often because of the journal's word count limits. It may be ideal to include tables or charts in-line in the article, but if there's no room, the appendix can provide extra space.

Handling data: A workflow for dealing with data in your SI

Submission and sharing of data are especially key steps in dealing with your SI in appendixes, annexes, and other formats. When you're submitting your article to a journal, there is a common workflow for this:

1. Create additional supplementary files (usually as few as possible, a single file is ideal).
2. Upload to the journal site or one of the many ‘approved' online data repositories.
3. You'll be given a URL to link back to your data files.
4. Add this link to the Acknowledgements section of your paper with some text such as “Additional files in support of this article can be found at https://...”

Some commonly used and ostensibly approved online data repositories:

• figshare
• Harvard Dataverse
• Open Science Framework (OSF)
• Mendeley Data
• Zenodo

But don't get carried away!

Supplementary information, including appendixes and annexes, can also be abused. Additional information may be so long/big/dense that it actually may not undergo full peer review even though the rest of the article does.

A study by Pop and Salzberg asserted that journals' word restrictions may cause authors to move key information outside the main manuscript body. In this way, it can avert proper peer review while also being less accessible to the reader. This hinders further investigation because readers have to wade through huge amounts of supplementary documents to find what they're after.

It also robs authors cited in the supplementary information of the recognition they would receive from citations in the body text.

Nature commendably lays out specifics for SI – check them here.

Final thoughts

If you're unsure of what needs to be in your supplementary information, or if you even need an appendix or annex, as well as the English quality and style, a scientific edit can be a big help. Explore AJE's extensive editing services here.