When do I use et al. in APA 7?

For any work with three or more authors, from the very first citation: (Piwowar et al., 2018). This applies even to the first citation, which is a change from the sixth edition. Works with one or two authors always show every name.

Does et al. go in the reference list?

Not in APA, which lists up to 20 authors and uses an ellipsis for longer lists. MLA does use et al. in the works-cited list for three or more authors. Chicago 18 uses it in the bibliography only for works with more than six authors, and IEEE only for more than six.

Is there a period after et al.?

Yes, after al. and never after et. It stands for the Latin et alia, and al. is an abbreviation while et is a whole word. In APA, a comma follows when a year comes next: (Piwowar et al., 2018). It is not italicized in APA, MLA or Chicago; many Harvard guides do italicize it.

How do I cite two works by the same author from the same year?

Add lowercase letters to the year: (Surname, 2020a) and (Surname, 2020b). In APA the letters are assigned in the order the works appear in the reference list, which is alphabetical by title. The letters appear in the reference list as well.

What did Chicago 18 change about multiple authors?

The manual's What's New page for the 18th edition says that up to six authors are now listed in a bibliography or reference-list entry; if there are more than six, only the first three are listed, followed by et al. In a note or an author-date text citation, up to two authors are listed; if there are more than two, only the first is given, followed by et al.

How to Cite Multiple Authors, Et Al., and Same Author Same Year

Author rules are where citation styles disagree most, and where the recent editions changed most. APA 7 (2019) and Chicago 18 (2024) both moved the "et al." threshold, so advice written before those editions is often out of date.

The Rules at a Glance

In-text citations and notes:

Style	1 author	2 authors	3 authors	4 or more
APA 7	(Cowan, 2001)	(Watson & Crick, 1953)	(Aron et al., 2019)	et al.
MLA 9	(Cowan 87)	(Watson and Crick 737)	(Aron et al. 350)	et al.
Chicago 18	Cowan	Watson and Crick	Aron et al.	et al.
Harvard (Cite Them Right)	(Cowan, 2001)	(Watson and Crick, 1953)	(Aron, Botella and Lubart, 2019)	et al.
IEEE	Cowan [1]	Watson and Crick [2]	Aron et al. [3]	et al.

Reference list or bibliography:

Style	How many authors are listed
APA 7	Up to 20. For 21 or more: the first 19, an ellipsis, then the last author.
MLA 9	One or two in full. For three or more: the first author followed by "et al."
Chicago 18	Up to six. For more than six: the first three followed by "et al."
Harvard (Cite Them Right)	All authors, unless your institution's guide allows "et al." for four or more
IEEE	Up to six. For more than six: the first author followed by "et al."

IEEE citations are numbers, so author names appear in the text only when you choose to mention them. The IEEE Reference Guide says to use "et al." in the text when a reference has three or more names.

Worked Example: Nine Authors

The example is a real article with nine authors: Piwowar, Priem, Larivière, Alperin, Matthias, Norlander, Farley, West and Haustein, "The State of OA", published in PeerJ in 2018.

APA: Piwowar, H., Priem, J., Larivière, V., Alperin, J. P., Matthias, L., Norlander, B., Farley, A., West, J., & Haustein, S. (2018). The state of OA: A large-scale analysis of the prevalence and impact of open access articles. PeerJ, 6, Article e4375. https://doi.org/10.7717/peerj.4375
In-text: (Piwowar et al., 2018)
MLA: Piwowar, Heather, et al. "The State of OA: A Large-Scale Analysis of the Prevalence and Impact of Open Access Articles." PeerJ, vol. 6, 2018, e4375, https://doi.org/10.7717/peerj.4375.
In-text: (Piwowar et al.)
Chicago bibliography: Piwowar, Heather, Jason Priem, Vincent Larivière, et al. "The State of OA: A Large-Scale Analysis of the Prevalence and Impact of Open Access Articles." PeerJ 6 (2018): e4375. https://doi.org/10.7717/peerj.4375.
Note: 1. Heather Piwowar et al., "The State of OA," ...
Harvard: Piwowar, H., Priem, J., Larivière, V., Alperin, J.P., Matthias, L., Norlander, B., Farley, A., West, J. and Haustein, S. (2018) 'The state of OA: a large-scale analysis of the prevalence and impact of open access articles', PeerJ, 6, e4375. Available at: https://doi.org/10.7717/peerj.4375
In-text: (Piwowar et al., 2018)
IEEE: [1] H. Piwowar et al., "The state of OA: A large-scale analysis of the prevalence and impact of open access articles," PeerJ, vol. 6, Feb. 2018, Art. no. e4375, doi: 10.7717/peerj.4375.

Name Order and Punctuation

APA: every author is inverted (Surname, Initials). An ampersand comes before the last author, in the reference and in parenthetical citations. In a sentence, write "and": Watson and Crick (1953).
MLA and Chicago: only the first author is inverted. The rest are written normally: Watson, J. D., and F. H. C. Crick.
Harvard: all inverted, joined with "and", no ampersand.
IEEE: initials first, never inverted: J. D. Watson and F. H. C. Crick.

Keep the authors in the order printed on the source. The order signals contribution and is not yours to rearrange.

Twenty-One or More Authors in APA

Large collaborations in physics, genomics and medicine can have hundreds of authors. APA lists the first 19, inserts an ellipsis with no ampersand, and ends with the final author:

Author, A. A., Author, B. B., Author, C. C., [authors 4 through 18], Author, S. S., . . . Author, Z. Z. (Year). Title of article. Journal, volume(issue), pages. DOI

When a named group is the author (for example a consortium credited on the byline), use the group's name as the author.

Same Author, Same Year

Add a lowercase letter after the year, in both the citation and the reference list.

APA reference list:
[Surname, A. A.] (2020a). [Title that comes first alphabetically]. ...
[Surname, A. A.] (2020b). [Title that comes second alphabetically]. ...
In-text: ([Surname], 2020a, 2020b)

This is a template: fill the bracketed parts with your own sources. APA assigns the letters by alphabetical order of title, ignoring "A" and "The". For undated works the form is (Surname, n.d.-a). Chicago author-date and Harvard use the same letter system. MLA has no years in its citations, so it adds a short title instead: (Surname, Short Title 14). In IEEE each work simply has its own number.

Several Works by the Same Author

APA and Harvard: order the entries by year, earliest first. In one citation, give the name once: (Surname, 2018, 2020a, 2022).
MLA: alphabetize by title. From the second entry on, replace the author's name with three hyphens or three em dashes followed by a period.
Chicago 18: the 18th edition now prefers repeating the author's name in each bibliography entry. The 3-em dash used in earlier editions is no longer recommended.

When Et Al. Creates Ambiguity

If two works from the same year shorten to the same citation, because they share a first author and both become (First author et al., Year), APA says to write out as many names as it takes to tell them apart, followed by "et al.":

([Author 1], [Author 2], [Author 3], et al., [Year])
([Author 1], [Author 2], [Author 4], et al., [Year])

"Et al." is plural, so it must stand for at least two people. If only one name would remain, write that name out.

Authors With the Same Surname

APA adds the first author's initials in every in-text citation when two first authors share a surname, even when the years differ: ([A. B. Surname] & [Coauthor], [Year]; [C. Surname], [Year]). MLA adds the first initial, or the full first name if the initials also match.

Organizations as Authors

Write the full name the first time. If the organization has a well-known abbreviation, APA introduces it in the first citation and uses it afterwards: (World Health Organization [WHO], 2026), then (WHO, 2026). The reference list uses the full name.

Common Mistakes

Following the older APA rule and listing several authors at first mention
Writing "et. al", "et al" or "et all"
Using "et al." for a work with two authors
Using "&" in a sentence, or "and" inside APA parentheses
Truncating the APA reference list to "et al."
Applying the 17th edition's author limits when your department has moved to the 18th edition
Reordering authors alphabetically

Sources for These Formats

APA Style, "Author–Date Citation System", "Elements of Reference List Entries" and "Citing Multiple Works" (apastyle.apa.org)
MLA Handbook, 9th ed., and MLA Style Center guidance on et al. and on multiple works by one author (style.mla.org)
The Chicago Manual of Style, 18th ed., "What's New in the 18th Edition" and Citation Quick Guide (chicagomanualofstyle.org)
Pears and Shields, Cite Them Right; University College Dublin Library, Harvard style guide
IEEE Reference Guide, version 3.28.2025, sections I and II

Full style rules: APA, MLA, Chicago, Harvard, IEEE.

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