Citation Style Guide

Chicago Style — Complete Citation Guide

Two systems in one: Notes-Bibliography for humanities (history, arts, literature) and Author-Date for sciences and social sciences. 17th edition (2017).

In this guide
Chicago overview — two systems Notes-Bibliography system Footnotes & endnotes Ibid. and shortened notes N-B examples (book, journal, website) Author-Date system A-D examples Common mistakes

Chicago style — two systems

Chicago Style (published by the University of Chicago Press) is one of the most comprehensive style guides. The 17th edition (2017) offers two distinct citation systems, and which one you use depends on your discipline:

📜 Notes-Bibliography (N-B)

Used in humanities — history, art history, literature, music, film. Uses numbered footnotes or endnotes in the text, plus a Bibliography at the end. Allows for extended commentary in notes.

🔬 Author-Date (A-D)

Used in social sciences, physical sciences, and some humanities. Uses in-text parenthetical citations (Author, Year) — similar to APA/Harvard. Full details in a Reference List at the end.

If your instructor has not specified which system to use, check which is standard in your discipline and confirm with them. History and arts → N-B; social sciences → Author-Date. Never mix the two systems in the same paper.

Notes-Bibliography (N-B) system

In the N-B system, every source is cited with a superscript number in the text (¹). This number corresponds to a footnote at the bottom of the page or an endnote at the end of the document. A Bibliography at the end of the paper lists all sources alphabetically.

The note and bibliography formats differ in small but important ways — primarily author name order (First Last in notes; Last, First in bibliography) and punctuation.

Footnotes and endnotes

Ibid. and shortened notes

Shortened notes — how subsequent citations work

Full first note: Henry L. Roediger and Andrew C. Butler, "The Critical Role of Retrieval Practice in Long-Term Retention," Trends in Cognitive Sciences 15, no. 1 (2011): 24.

Shortened subsequent note (same source, different page): Roediger and Butler, "The Critical Role," 26.

Ibid. (same source AND same page as immediately preceding note): Ibid.

Ibid. (same source, different page): Ibid., 28.

Note: Ibid. can only be used when the immediately preceding note cites the same source. If any other source intervenes, use the shortened form.

N-B examples

Book — N-B

Book
Note (first citation)
1. Peter C. Brown, Henry L. Roediger III, and Mark A. McDaniel, Make It Stick: The Science of Successful Learning (Cambridge, MA: Harvard University Press, 2014), 28.
Shortened note
2. Brown, Roediger, and McDaniel, Make It Stick, 45.
Bibliography entry
Brown, Peter C., Henry L. Roediger III, and Mark A. McDaniel. Make It Stick: The Science of Successful Learning. Cambridge, MA: Harvard University Press, 2014.

Journal article — N-B

Journal Article
Note (first citation)
3. Henry L. Roediger and Andrew C. Butler, "The Critical Role of Retrieval Practice in Long-Term Retention," Trends in Cognitive Sciences 15, no. 1 (2011): 20–27.
Bibliography entry
Roediger, Henry L., and Andrew C. Butler. "The Critical Role of Retrieval Practice in Long-Term Retention." Trends in Cognitive Sciences 15, no. 1 (2011): 20–27. https://doi.org/10.1016/j.tics.2010.09.003.

Website — N-B

Website
Note
4. World Health Organization, "Mental Health Action Plan 2013–2030," March 14, 2023, https://www.who.int/publications/i/item/9789240031029.
Bibliography entry
World Health Organization. "Mental Health Action Plan 2013–2030." March 14, 2023. https://www.who.int/publications/i/item/9789240031029.

Author-Date (A-D) system

The Author-Date system uses in-text parenthetical citations — very similar to APA — with a Reference List at the end. The key difference from the N-B system is that notes are not used; instead, all citations appear parenthetically in the text itself.

In-text citation — Author-Date

Examples
Retrieval practice significantly improves long-term retention (Roediger and Butler 2011, 24).
Note: Unlike APA, Chicago Author-Date does NOT use a comma between author and year: (Smith 2020) not (Smith, 2020).

Journal article — Author-Date reference list

Reference List — Journal Article
Author Last, First, and First Last. Year. "Title of Article." Journal Name Volume (Issue): Pages. DOI.
Roediger, Henry L., and Andrew C. Butler. 2011. "The Critical Role of Retrieval Practice in Long-Term Retention." Trends in Cognitive Sciences 15 (1): 20–27. https://doi.org/10.1016/j.tics.2010.09.003.

Book — Author-Date reference list

Reference List — Book
Brown, Peter C., Henry L. Roediger III, and Mark A. McDaniel. 2014. Make It Stick: The Science of Successful Learning. Cambridge, MA: Harvard University Press.

Common Chicago mistakes

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