Chicago author-date style places a short citation, author and year, in the text and full details in a reference list. It is the Chicago option favored in the social and natural sciences.
This page follows the 18th edition of The Chicago Manual of Style (2024). Where the 17th edition differed and many instructors still use it, the difference is noted.
Chicago Author-Date at a Glance
In the text: (Author Year, page), for example (Okafor 2021, 34), with no comma between author and year. In the reference list: Author. Year. Title. Publication details. Entries are alphabetical by author surname, with the year directly after the name.
In text: (Hartley and Mensah 2022, 118)
Reference: Hartley, Fiona, and Kwame Mensah. 2022. Care Work and the State. University of Chicago Press.
Author-Date Versus Notes and Bibliography
| Author-date | Notes and bibliography | |
|---|---|---|
| Citation in text | Parenthetical (Author Year, page) | Superscript number with footnote or endnote |
| End list | References | Bibliography |
| Year position | Directly after author | Near the end of the entry |
| Typical fields | Social sciences, sciences | History, arts, humanities |
Use whichever your instructor or journal specifies, and never mix the two systems in one paper.
In-Text Citations
Place the citation at the end of the clause or sentence it supports, before the full stop. Include a page number when you quote or refer to a specific passage.
| Situation | Format |
|---|---|
| One author | (Okafor 2021, 34) |
| Two authors | (Hartley and Mensah 2022) |
| Three or more authors (18th edition) | (Lindqvist et al. 2020) |
| Author named in sentence | Okafor (2021, 34) argues that... |
| Same author, same year | (Okafor 2021a, 2021b) |
| Several sources | (Okafor 2021; Lindqvist et al. 2020) |
| No date | (Ruiz, n.d.) |
| Organization as author | (World Health Organization 2023) |
For a page range, use an en dash and the shortened form Chicago prefers, as in (Okafor 2021, 34–36). For sources without page numbers, you can cite a chapter or section heading instead, or simply omit the locator.
The 17th edition used "et al." in text only for four or more authors, listing all three names for three-author works. Check which edition you are asked to follow.
Reference List Rules
- Title the list "References" and place it at the end of the paper.
- Arrange entries alphabetically by the first author's surname.
- Invert only the first author's name: Hartley, Fiona, and Kwame Mensah.
- For works by one author, list them in chronological order, earliest first.
- Use a hanging indent for each entry.
- In the 18th edition, list up to six authors; for seven or more, list the first three followed by et al.
- Use headline-style capitalization for titles of books, articles and journals.
Books and Chapters
Book: Okafor, Ngozi. 2021. Migration and Belonging in Urban Africa. Oxford University Press.
Edited book: Ruiz, Ana, ed. 2019. Methods for Community Health Research. Routledge.
Chapter in edited book: Brennan, Siobhan. 2019. "Participatory Approaches in Rural Clinics." In Methods for Community Health Research, edited by Ana Ruiz, 77–102. Routledge.
The 18th edition no longer requires the place of publication, and the examples above omit it. The 17th edition included it, for example "New York: Routledge". Follow your instructor's edition.
Journal Articles
Give the article title in quotation marks, the journal in italics, then volume, issue in parentheses, page range and DOI if available.
Lindqvist, Erik, Mei Chen, and Paul Adeyemi. 2020. "Shift Length and Medication Errors in Acute Care." Journal of Nursing Management 28 (6): 1314–22. https://doi.org/10.1111/jonm.00000.
In text: (Lindqvist et al. 2020, 1318)
The DOI in this example is illustrative. Present a DOI as a full URL beginning https://doi.org/. If there is no DOI, give a stable URL for online articles or the database name.
Websites and Online Sources
Web page with author: Patel, Ravi. 2023. "Rethinking Hospital Discharge." Health Policy Review, March 14, 2023. https://www.example.org/discharge.
Organization as author: World Health Organization. 2023. "Hand Hygiene in Health Care." https://www.example.org/hand-hygiene.
No date: Ruiz, Ana. n.d. "Community Health Worker Toolkit." Accessed May 2, 2026. https://www.example.org/toolkit.
Chicago recommends an access date only when a source has no publication or revision date. The URLs here are placeholders.
Common Chicago Author-Date Errors
| Error | Correct form |
|---|---|
| (Okafor, 2021) | (Okafor 2021) |
| Year at the end of the reference | Year directly after the author's name |
| Inverting every author's name | Invert the first author only |
| Mixing footnotes with author-date | Use one system throughout |
| Page range with "pp." in reference list | Page range without "pp." |
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Frequently Asked Questions
A Chicago citation system that uses parenthetical (Author Year, page) citations in the text and a full reference list at the end, common in the social and natural sciences.
No. Write (Okafor 2021), not (Okafor, 2021). A comma separates the year from the page number: (Okafor 2021, 34).
In the 18th edition, use et al. in text for three or more authors. The 17th edition used it for four or more.
The 18th edition, published in 2024. Some instructors still require the 17th, so check your guidelines.
Not in the 18th edition, which makes it unnecessary. The 17th edition included it.
Only when the source has no publication or revision date, or if your instructor asks for them.
Chicago discourages secondary citation. If you cannot consult the original, cite it as "quoted in" the source you read, and list the source you actually used in your references.
Author-date uses a reference list of cited works with the year after the author. Notes and bibliography uses a bibliography, often including works consulted, with the year near the end.