Chicago Style Citation: Which of the Two Systems Do You Actually Need?

The Chicago Manual of Style (18th edition) lays out two distinct ways to cite sources, and it's explicit that neither one is "more correct" than the other — they're built for different kinds of writing. The Notes-Bibliography system cites sources with numbered footnotes or endnotes (a raised superscript number in the text, with the full citation at the bottom of the page or end of the paper), backed by a separate bibliography. Chicago's own guidance describes this as its oldest and most flexible option, and it's the standard choice in the humanities — literature, history, the arts.

The Author-Date system instead cites sources in parentheses right in the sentence — author's last name and publication year, like (Smith 2012), or (Smith 2012, 21–22) with a page number — matched to an alphabetized reference list at the end. This is the system Chicago itself describes as preferred in the sciences and social sciences, where publication date matters more to the reader than it does in a humanities paper.

In Notes-Bibliography, a first footnote reference might read: 1. Gabriel García Márquez, Love in the Time of Cholera, trans. Edith Grossman (London: Cape, 1988), 24. — with a shortened version used for any repeat citation of the same source, and a full bibliography entry at the end formatted slightly differently again (author's last name first, for alphabetizing).

In Author-Date, the same source appears in the reference list as: García Márquez, Gabriel. 1988. Love in the Time of Cholera. Translated by Edith Grossman. London: Cape. — alphabetized by author, no footnotes at all, with every in-text mention just the parenthetical author-year instead. The underlying source information is the same in both systems; only where and how it's presented changes.

Chicago doesn't default to one system over the other, so check your assignment sheet, your department's style guide, or your target journal's author guidelines before you format anything — an English literature essay almost always means Notes-Bibliography, while a psychology or biology paper more often means Author-Date, but that's a general pattern, not a rule, and it's always worth confirming directly.

StudyPilot's citation generator supports Chicago as one of its built-in styles alongside APA, MLA, Harvard, IEEE, and Vancouver, which handles the mechanical parts — author order, italics, punctuation — once you've confirmed your source details. Since Chicago covers two structurally different systems, it's still worth a quick check that the output matches whichever one (Notes-Bibliography or Author-Date) your instructor actually asked for before you turn in a final draft.