How Do You Use et al. in Scientific Papers? (with many examples)

In scholarly papers, citation rules definitely have some strange terms. Some aren't English, and some aren't words. The term “et al.”, for instance, isn't an English word. For someone who speaks a non-Latin-origin language, like Japanese or Arabic, it's especially confusing. This post explains the use of et al. and some common mistakes related to it.

You use “et al.” in academic writing to cite a publication that has multiple authors (or other contributors, such as editors). For example, instead of an in-text citation reading (Schouten, McAlexander, Smith, Rogers, & Koenig 2010), it would simply be (Schouten et al., 2010).

Et al. is used in manuscript body text and in reference lists and footnotes. Exactly how and where to use it varies depending on the prescribed style, such as APA, AMA, Harvard, Vancouver, or that of a specific publication. It's short for et alia (or the respective masculine and feminine plural et alii or et aliae) – Latin for “and others.” The abbreviation is required, but it also makes writing easier to read, helping the reader find the cited works faster.

Even experienced authors have trouble with “et al.” because many major academic writing style guides, as well as specific journals, use it slightly differently. Let's look at the main ones you'll typically see when you're seeking to publish your scientific manuscript. Some of these styles are updated regularly, so always be sure to check with your professor and/or with your target publication's guidelines.

Using et al. in the main academic referencing styles

The following sections will show how to use “et al.” in APA, MLA, Vancouver, and other main referencing styles, especially those found in journals.

APA (American Psychological Association) Style

APA is commonly used in the social sciences and medicine, both in universities and in publications. Keep up to date on the latest APA style as well.

For in-text citations in APA Style, when a source has two authors, list both authors by their last names, followed by the publication year. For three or more authors, cite the first author followed by “et al.”

Note that these rules are based on the Publication Manual of the American Psychological Association, Seventh Edition (APA 7). The previous versions required listing more authors in the in-text citations, and had some differences in the reference list requirements.

APA Style in-text citations

The main difference in APA Style in-text citations is their use of the ampersand (&) symbol. Et al. is now simply used for three-plus authors. It used to be more confusing, as up to five authors were listed at first reference and then et al. on second reference. Many will not be familiar with the current style, so be sure to check.

APA Style reference list

The “et al.” abbreviation is not used in the APA references list. But knowing how to prepare the list can help you know when to use et al. in the in-text citations.

For publications with 3–20 authors put all the authors. For example:

Eckhardt, G., Houston, M., Jiang, B., Lamberton, C., Rindfleisch, A. & Zervas, G. (2019). Marketing in the sharing economy. Journal of Marketing, 83(5), 5-27.

For a source with 20 or more authors put the first six authors, followed by an ellipsis (…) and then the final author. For example:

Pegion, K., Kirtman, B. P., Becker, E., Collins, D. C., LaJoie, E., Burgman, R., . . . Kim, H. (2019). The subseasonal experiment (SubX): A multimodel subseasonal prediction experiment. Bulletin of the American Meteorological Society, 100(10), 2043-2061.

APA Style is rather idiosyncratic with its combinations of spaces and commas. Be careful with those, especially if you have a picky adviser or run into a picky peer reviewer or journal editor.

MLA (Modern Language Association) Style

MLA Style is most commonly used in the humanities. Nothing makes it especially unique, but it has its own slight differences.

MLA Style in-text citations

Unlike APA Style, MLA Style doesn't use the year in the citation. Instead, it uses the authors' last names and the relevant page number.

Use “et al.” for sources with three or more authors for both in-text citations and in the references list.

MLA Style reference list

For the reference list, known as the Works Cited list in MLA Style, publications with three or more authors will look like this:

Wysocki, Anne Frances, et al. Writing New Media: Theory and Applications for Expanding the Teaching of Composition. Utah State University Press, 2004.

Vancouver Style

The Vancouver Style guide was developed in Canada by the International Committee of Medical Journal Editors (ICMJE). It's now widely used for journal referencing in medicine, health sciences, and life sciences, and even in technology.

It's a concise style that works well for hyperlinking and with referencing software such as EndNote.

Vancouver Style in-text citations

Vancouver Style uses numbers for in-text citations, so using “et al.” is not a concern. However, if an author is named in a sentence, use “et al.” for publications with more than one author. For example:

“Holt et al. found that there was no histochemical evidence of mitochondrial myopathy.”

Vancouver Style reference list

For the reference list, put the names of up to six authors. For example:

Holt IJ, Miller DH, Harding AE. Genetic heterogeneity and mitochondrial DNA heteroplasmy in Leber's hereditary optic neuropathy. J Med Genet. 1989 Dec; 26 (12): 739-743.

For seven or more authors put the first six and “et al.” For example:

Meakin CJ, King DA, White J, Scott JM, Handley H, Griffiths A, et al. Screening for depression in the medically ill. J Nerv Ment Dis 1991; 12: 45‐53.

AMA (American Medical Association) Style

Also very common in medical referencing is AMA Style. AMA Style tends to be used for strictly clinical medical journals and the life sciences.

AMA Style In-text citations and reference list

The AMA system is similar to the Vancouver system in that it also uses numbers for in-text citations. The difference is found in the way AMA treats publications with seven or more authors in the reference list.

In AMA put the names of all the authors for up to six authors. For example:

Mizumoto K, Kagaya K, Zarebski A, Chowell G. Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020. Euro Surveill. 2020;25(10):2000180.

For seven or more authors put the first three, followed by “et al.” For example:

Ahn DG, Shin HJ, Kim MH, et al. Current Status of Epidemiology, Diagnosis, Therapeutics, and Vaccines for Novel Coronavirus Disease 2019 (COVID-19). J Microbiol Biotechnol. 2020;30(3):313-324.

Chicago/Turabian Style

Chicago Style (and the very similar Turabian Style) is an American English style guide that is widely used in books in the social sciences and humanities, as well as journalism. It's less commonly used in journals.

The massive and comprehensive book called The Chicago Manual of Style (CMOS) has two referencing systems: author-date and notes and bibliography (which, by the way, LaTex can handle automatically).

Chicago Style in-text citations

Use of “et al.” is the same in both of the above referencing styles. For in-text citations put all last names when there are up to three authors. For four or more authors put the first author's name followed by “et al.”

For footnotes, but the full author name(s). Note that relevant page numbers are also usually given in Chicago Style. Also, unlike APA Style, the word “and” is used instead of the & ampersand symbol. Footnotes are usually indicated in the text with a superscript number.

Chicago Style reference list

For the reference list in Chicago Style, use all authors' full names if the source has up to 10 authors. For example:

Sechzer, Jeri A., S. M. Pfaffilin, F. L. Denmark, A. Griffin, and S. J. Blumenthal, eds. Women and Mental Health. Baltimore: Johns Hopkins University Press, 1996.

For more than 10 authors put the first seven, followed by “et al.”

Harvard Style

This style guide will be familiar for students who have studied in the US or under US professors. It's commonly used from the high school level upward. It's less common in scientific publications.

Harvard Style in-text citations

For in-text citations in Harvard Style put all names if the source has three or fewer authors. Use “et al.” if there are four or more authors. Just to make things even more confusing, Harvard usually does not put a comma between the author name or between “et al.” and the year.

Harvard Style reference list

For the reference list in Harvard Style put the names of all the authors, no matter how many there are. For example:

Lupien, S.J., McEwen, B.S., Gunnar, M.R. and Heim, C., 2009. Effects of stress throughout the lifespan on the brain, behaviour and cognition. Nature Reviews Neuroscience, 10(6), pp. 434-445.

Harvard style is primarily used in university settings, and each school may have its own variations. Be sure to check, because Harvard shows a lot of variety in punctuation and capitalization depending on the university or publication using it.

Specific journal variations

Despite the great number of referencing styles available, some journals prefer to use their own style of referencing. These are almost never 100% unique. Most often, they are based on a popular style, but with a few alterations.

Most commonly, Vancouver Style is used as a basis for making a publication's or journal's “house style” (see more on that topic below). Some add spaces. Some change the punctuation. Some use superscript numbers while others use numbers in parentheses or brackets.

For instance, the popular online open-access (OA) journal PLOS ONE states it uses Vancouver Style. It does, but it also places citation numbers in brackets and it removes spaces in some punctuation in the reference list. These are small differences, but an author must do them correctly or they risk having their submission rejected by their target journal.

Another example, the American Society of Agricultural and Biological Engineers (ASABE), which produced journals including Transactions of the ASABE, uses a variation of APA Style 6th Edition. Why? We may never know. But if you're submitting to them, you must follow their guidelines.

To be sure you satisfy the guidelines you can hire a professional scientific editor who has done this task hundreds, even thousands, of times. We're skilled at spotting tiny differences in styles. It's part of an editor job.

Common mistakes in using et al. in academic writing

There are several common mistakes that authors of any level should be aware of when using et al.

Using et al. when you shouldn't

Knowing where you should and should not put et al. depends on the style guide you're following. That's all. However, some authors simply put use et al. when there's more than one author. That's just wrong.

The recent APA Style update also made things confusing for students and publication-seeking researchers, because some professors and journal reviewers will be following APA 6 while others will be updated to APA 7. Still others may not care. If you're not sure, ask.

Using the period in et al.

Maybe the most common problem in using et al. is knowing where to put the period. It should be after the “al.” and not after the “et”. This is because, as mentioned, “et al.” is an abbreviation of the Latin phrase “et alia.” The “et” is itself a word.

The “et al.” may be followed by any other punctuation. For example:

(Aaker et al., 2004)

Or it may not. It depends on the publication.

When et al. ends a sentence, use only one period. For example:

“This leads to a 40% reduction in food waste, as shown by Simpson et al.”

“Et al.” vs. “etc.”

“Et al.” and “etc.” are sometimes confused with each other. But they're completely different.

The abbreviation “et al.” is used for lists of authors (or other contributors). That's all. However, “etc.” (et cetera, which is the Latin word for “and other similar things”) is used for lists or related items. For example:

“Riches et al. (2017) suggest that subcultures form around a variety of popular music styles (punk, hip hop, etc.), each with its own aesthetics and ethos.”

Final words on et al.

Although the basic concept behind using “et al.” is easy, each system is different. For journal submission, check the specifics. The journal may use a common style such as APA or Vancouver, but with a few custom differences. Some journals are very picky about this, some are not.

Even though the abbreviation is required, it adds readability. Modern scientific writing should be accessible and readable; so et al., though tricky, is a good thing.

If you need formatting for your manuscript to be sure you're using the right guidelines, scientific editors can do that for you. Journal guidelines are notoriously quirky and if English isn't your first language, they're even harder.

Professional scientific editors are trained in dealing with this. Many of us even enjoy it! Get a professional edit if you want to be sure you have your references totally consistent and pleasing to the journal editor's discerning eyes.

About the author

Adam Goulston is a U.S.-born, Asia-based science marketer, writer, and editor. His company, Scize, helps scientific businesses and researchers communicate their value globally. He has edited more than 3,000 scientific manuscripts.