Et Al.: Meaning, Usage and Rules in APA, MLA and Chicago
Et al. is one of the most used abbreviations in academic citation, and one of the most frequently misunderstood. Students confuse when to use it, whether it gets a period, whether it should be italicized, and how the rules differ between APA, MLA, and Chicago. This guide answers all of it. For a general overview of citation styles and when to use them, see our guide on how to cite sources.
Quick Answer
Et al. is a Latin abbreviation meaning "and others." In academic citations, it stands in for co-authors when a source has multiple authors. In APA 7th edition, use et al. for any source with three or more authors, from the very first citation. In MLA 9th edition, use et al. for sources with three or more authors in both the in-text citation and Works Cited entry. In Chicago style, use et al. in footnotes when a source has more than two authors, and in the bibliography for sources with more than six authors. Always write et al. with a period after "al" and without italics.
What Does Et Al. Mean?
Et al. is an abbreviation of the Latin phrase et alii (masculine), et aliae (feminine), or et alia (neuter), all meaning "and others." In academic writing, it stands in for the names of co-authors beyond a specified number, keeping citations readable without listing every contributor each time.
The abbreviation has two parts:
- et: the Latin word for "and" (no period, it is a complete word)
- al.: short for alii/aliae/alia (always followed by a period, because it is abbreviated)
This is why the correct form is always et al. with a period after "al" and no period after "et." Writing "et. al." or "et. al" or "etal" are all incorrect.
How to Write Et Al. Correctly
Before getting into the style-specific rules, these formatting principles apply in every context:
| Question | Answer |
|---|---|
| Period after "et"? | No. "Et" is a complete word. |
| Period after "al"? | Yes, always. It is an abbreviation. |
| Italics? | No. Et al. is not italicized in APA, MLA, or Chicago. |
| Comma before et al.? | No comma between the first author's name and et al. |
| Capitalized at start of sentence? | Only "Et" is capitalized: "Et al. (2021) found..." |
| Can et al. stand for one name? | No. Et al. is plural ("and others") and must represent at least two omitted names. |
Correct: Smith et al. (2021) Incorrect: Smith, et al. (2021) [incorrect: no comma between name and et al.] Incorrect: Smith et al. (2021) [incorrect: no italics] Incorrect: Smith et. al. (2021) [incorrect: no period after "et"] Incorrect: Smith et al (2021) [incorrect: period after "al" is required]
Et Al. in APA 7th Edition
In APA 7, the rule is clear-cut. For any work with three or more authors, you use et al. in every in-text citation, including the first one in your paper. This is a change from APA 6th edition, which required listing all authors up to five on the first citation.
APA In-Text Citation Rules
| Number of authors | In-text format |
|---|---|
| 1 author | (Smith, 2021), every time |
| 2 authors | (Smith & Jones, 2021), every time |
| 3 or more authors | (Smith et al., 2021), from the first citation onward |
APA In-Text Examples
One author:
(Sapolsky, 2017)
Two authors:
(Watson & Crick, 1953)
Three or more authors:
(Jerrentrup et al., 2018)
Narrative citation with three or more authors:
Jerrentrup et al. (2018) found that...
APA Reference List Rules
Et al. is used only for in-text citations in APA 7th edition. References in APA 7 do NOT use the phrase "et al."
In the reference list, include all authors up to 20. When a work has 21 or more authors, per the APA Style blog, list the first 19 authors, insert an ellipsis (...), and then give the final author's name. Et al. does not appear in the APA reference list.
APA reference list with 3 authors (all listed):
Jerrentrup, A., Mueller, T., Glowalla, U., Herder, M., Henrichs, N., Neubauer, A., & Schaefer, J. R. (2018). Teaching medicine with the help of "Dr. House." PLOS ONE, 13(3), Article e0193972.
When Two Sources Abbreviate to the Same Et Al. Form
If you cite two sources with the same first author and the same year, and both shorten to the same et al. form, you must disambiguate. Per the APA Style guidance on ambiguous et al. citations, include enough author names to make the two citations distinguishable:
Kapoor, Bloom, Montez, et al. (2017) Kapoor, Bloom, Zucker, et al. (2017)
Et Al. in MLA 9th Edition
In MLA 9th edition, et al. applies to sources with more than two authors, in both the in-text citation and the Works Cited entry. This is confirmed by the MLA Style Center.
MLA In-Text Citation Rules
| Number of authors | In-text format |
|---|---|
| 1 author | (Smith 42) |
| 2 authors | (Smith and Jones 42) |
| 3 or more authors | (Smith et al. 42) |
Note: in MLA, use "and" between two author names in in-text citations, not an ampersand.
MLA in-text example:
(Armstrong et al. 15)
MLA narrative citation:
When citing in the main text rather than parenthetically, MLA recommends writing "and colleagues" or "and others" instead of et al.:
Armstrong and colleagues argue that...
MLA Works Cited Rules
In the Works Cited list, sources with more than two authors use et al. after the first author's name:
MLA Works Cited example:
Armstrong, Anne K., et al. Communicating Climate Change: A Guide for Educators. Cornell UP, 2018.
The first author's name is inverted (Last, First); "et al." follows without inversion.
Et Al. in Chicago Style (18th Edition)
Chicago style has different rules for footnotes and bibliographies, and the threshold for using et al. differs from APA and MLA. The current rules are from the Chicago Manual of Style 18th edition.
Chicago Footnote Rules
In a note, list only the first author, followed by "et al." for sources with three or more authors.
| Number of authors | Footnote format |
|---|---|
| 1-2 authors | List all authors |
| 3 or more authors | First author et al. |
Chicago footnote example (3+ authors):
- Jeri A. Sechzer et al., Women and Mental Health (Baltimore: Johns Hopkins University Press, 1996), 243.
Chicago Bibliography Rules
For three or more authors, list up to six in the bibliography; for more than six authors, list the first three, followed by "et al."
| Number of authors | Bibliography format |
|---|---|
| 1-6 authors | List all authors |
| 7 or more authors | First three authors, then et al. |
Chicago bibliography example (7+ authors):
Sechzer, Jeri A., S. M. Pfafflin, F. L. Denmark, A. Griffin, and S. J. Blumenthal, et al. Women and Mental Health. Baltimore: Johns Hopkins University Press, 1996.
Chicago Author-Date System
In the Author-Date system (used in social sciences), follow the same rules as for footnotes in in-text citations: first author et al. for three or more authors.
(Sechzer et al. 1996)
Comparison Table: Et Al. Rules by Style
| APA 7th | MLA 9th | Chicago 18th | |
|---|---|---|---|
| Threshold for et al. in text | 3+ authors | 3+ authors | 3+ authors |
| Applies from first citation? | Yes | Yes | Yes |
| Et al. in reference list? | No (list up to 20) | Yes (3+ authors) | Depends on author count |
| Reference list threshold | All up to 20; then 19 + last | 3+ → et al. | Up to 6; 7+ → first 3 + et al. |
| Narrative alternative | Not specified | "and colleagues" / "and others" | Not specified |
| Period after al.? | Yes | Yes | Yes |
| Italics? | No | No | No |
| Comma before et al.? | No | No | No |
Special Cases
Et Al. with Only Two Omitted Authors
Et al. is plural. It means "and others", not "and one other". Et al. cannot replace just one name. If a source has three authors, et al. stands for two omitted names, which is acceptable. If you are tempted to use et al. for a two-author source, do not: list both authors.
Same First Author, Different Years
If Smith published a paper in 2019 and another in 2022, both with multiple co-authors, the citations are distinguishable by year:
(Smith et al., 2019) and (Smith et al., 2022)
No additional disambiguation is needed.
Same First Author, Same Year, Different Co-Authors
This is the ambiguous case. In APA, include enough additional author names to make the citations distinguishable. In MLA and Chicago, the same logic applies.
Group or Organizational Author
Et al. is for human co-authors, not for organizational authors. If the author is a government agency, institute, or organization, spell it out (or use a standard abbreviation if one exists). Do not substitute et al. for organizational names.
Common Mistakes with Et Al.
1. Adding a comma before et al.
Smith, et al. (2021) is incorrect in all three styles. The correct form is Smith et al. (2021). There is no comma between the first author's name and et al.
2. Italicizing et al.
Et al. is not italicized in APA, MLA, or Chicago. It is treated as a regular part of the citation, not as a foreign phrase requiring special formatting.
3. Writing "et. al." with a period after "et"
Et is a complete Latin word, not an abbreviation. Only "al." gets a period. Writing "et. al." is incorrect.
4. Using et al. in the APA reference list
APA 7th edition does not use et al. in the reference list. List all authors up to 20. For 21 or more, use the first 19, an ellipsis, and the final name. Many students apply the in-text rule to the reference list incorrectly.
5. Using et al. for two-author sources
Et al. means "and others" (plural). It cannot stand for a single omitted name. A two-author source always has both names listed in full in every style.
6. Confusing APA 6th and 7th edition rules
In APA 6th edition, you listed all authors up to five on the first citation, then used et al. on subsequent citations. APA 7th edition simplified this: use et al. from the first citation for any source with three or more authors. Many students still apply the old rule.
7. Possessive form with et al.
When you need a possessive, write "Smith et al.'s study" with the apostrophe-s after the period of "al." Writing "Smith et al.s' study" is incorrect. That said, possessive constructions with et al. are awkward and best avoided altogether. Rephrase to "the study by Smith et al." or "Smith et al. (2021) found that..." wherever possible.
8. Confusing et al. with etc. or et alibi
Et al. refers to people. It is not interchangeable with:
- etc. (et cetera, "and the rest"): used when listing things, not people
- et alibi (et alibi, "and elsewhere"): used when listing places or locations
Writing "Smith, Jones, etc." in a citation is incorrect. The correct form is "Smith et al." when the omitted items are people.
Summary
Et al. means "and others" in Latin. It is always written with a period after "al." and without italics or a comma before it. In APA 7th edition, use et al. in text for any source with three or more authors, including the first citation; never use it in the reference list. In MLA 9th edition, use et al. for three or more authors in both in-text citations and the Works Cited entry. In Chicago 18th edition, use et al. in footnotes for three or more authors, and in the bibliography when a source has more than six authors. The most common mistakes are adding a comma before et al., italicizing it, writing "et. al." with a period after "et," and applying the outdated APA 6th edition rules. For a full overview of citation styles, see how to cite sources.