APA vs Chicago
APA and Chicago both cite sources, but they take very different routes. APA is an author-date style used mostly in the social sciences. Chicago offers two systems: a notes-and-bibliography style with footnotes that dominates in history and the humanities, and an author-date style that looks similar to APA and is common in some sciences.
| Dimension | APA | Chicago |
|---|---|---|
| Main disciplines | Psychology, education, social and health sciences | History, theology, some humanities and sciences |
| Current edition | APA 7th edition | Chicago Manual of Style 18th edition (2024) |
| Systems available | One: author-date | Two: notes-and-bibliography and author-date |
| In-text citation (most common use) | (Smith, 2020) | Footnote number referencing a full citation |
| Reference list title | References | Bibliography (notes style) or Reference List (author-date) |
| Footnotes for source credit | Not used | Central in notes-and-bibliography style |
What is APA?
APA is a single, parenthetical, author-date citation style used in the social and health sciences. Every in-text citation includes the author and the year, and every cited source appears in a References list at the end, alphabetized by author. APA is designed for fields that care strongly about recency — you should always be able to tell at a glance whether the cited work is from 1992 or 2023. The current edition is APA 7. Its conventions include sentence case for article and book titles in the reference list, title case for journal names, DOIs formatted as URLs, and running heads only when an instructor requires them. APA is the expected style for most quantitative papers in psychology, education, nursing, and communication.
What is Chicago?
Chicago is the style maintained by the University of Chicago Press. The current edition is the 18th, published in 2024. Chicago is unusual in that it offers two systems. The notes-and-bibliography style uses footnotes (or endnotes) to cite sources, with a full bibliography at the end. This system is standard in history, art history, theology, and much of the traditional humanities. Writers in these fields use footnotes not only for citations but often for asides and extended explanations. The second Chicago system is author-date, which looks similar to APA — (Smith 2020) in text, with a Reference List at the end. Author-date Chicago is used in some sciences and in interdisciplinary work. When people say ‘Chicago style,’ they usually mean notes-and-bibliography unless context makes it clear otherwise.
Key differences
The biggest day-to-day difference is what the reader sees on the page. APA puts the citation inline as (Author, Year). Chicago notes-and-bibliography puts a superscript number in the sentence and the full citation in a footnote, moving bibliographic detail out of the reading line. Chicago author-date, by contrast, looks very similar to APA. The second difference is the reference list. APA uses a References list with specific capitalization rules. Chicago notes-and-bibliography uses a Bibliography with its own punctuation conventions — for example, notes separate elements with commas while bibliography entries separate them with periods, and author names appear differently in each. Getting those punctuation details right is what separates a clean Chicago paper from one that has been compiled by hand and half-remembers the rules.
When to use which
Use APA when you are writing for a psychology, education, nursing, or social science course, or submitting to a journal in those fields. APA is also a reasonable default in quantitative communication and business research. Use Chicago notes-and-bibliography when you are writing for a history, theology, art history, or classics course — basically any humanities field where footnotes are expected. If your instructor talks about footnotes at all, they almost certainly mean Chicago. Use Chicago author-date only if the course or publication specifically requests it, since it overlaps so much with APA that most students default to APA when they want parenthetical citations. And as always, the syllabus overrides general disciplinary convention.
Examples
APA in-text: (Kahneman, 2011). References entry: Kahneman, D. (2011). Thinking, fast and slow. Farrar, Straus and Giroux. Chicago notes-and-bibliography, first footnote: 1. Daniel Kahneman, Thinking, Fast and Slow (New York: Farrar, Straus and Giroux, 2011), 34. Bibliography entry: Kahneman, Daniel. Thinking, Fast and Slow. New York: Farrar, Straus and Giroux, 2011. Notice the flipped author name in the bibliography, the comma-to-period shift from the note, and the absence of any parenthetical citation in the text — the footnote carries the weight. For later citations of the same source in Chicago, you usually use a shortened footnote form: 2. Kahneman, Thinking, Fast and Slow, 112. That shortened form is one of the small details that reference managers handle automatically but hand-typed papers often get wrong. Another common trap is forgetting the subsequent-bibliography rule — in a Chicago bibliography, entries use the author's last name first, but repeated authors on successive entries are replaced with a long em-dash in some Chicago variants and repeated in others, depending on the edition. When in doubt, check the current Chicago Manual of Style or your program's style guide rather than guessing from older examples.
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