Abbreviated Footnote in Chicago Style (18th ed.)

An abbreviated footnote in Chicago style, which the 18th edition calls a shortened note, is the compact form of a citation you have already given in full: the author’s last name, a shortened title and the page number. It replaces repeating the whole note, and in the 18th edition it also replaces most uses of “ibid.” This guide gives the format, a full-to-short conversion for each common source type, and a worked example of turning an “ibid.” run in a thesis chapter into shortened notes. For the full note that comes first, see Chicago footnote format.

The format

A shortened note has three parts, in this order, separated by commas and ending with a period (University of Portland library guide, 18th ed.):

Author’s last name only, with no first name or initials.
Shortened title: two to four keywords from the main title. The short form uses the main title, so the subtitle is dropped, and an initial “A”, “An” or “The” is omitted. Books and other whole works stay in italics; articles and chapters stay in quotation marks.
Page number of the passage you are citing.

The template is therefore: Surname, Short Title, page. Publisher, place, year and DOI belong to the full note and the bibliography entry, not the short form.

The manual treats shortened citations in CMOS 13.32 to 13.39. Per 13.32, you use the short form when the source has already been cited in full in an earlier note or has a full entry in the bibliography, and the short form must remind the reader of the full title or lead them to the bibliography entry. The usual short form is the author’s last name plus the main title (13.33).

How long is a “long” title?

The two Chicago 18th-edition library guides differ slightly on the threshold. Douglas College says titles are shortened if they run to more than four words; the University of Portland says to shorten titles of four words or more. A title shorter than that needs no cutting. Whichever you pick, apply it the same way to every source in the document.

Which form to use: a decision table

Situation	Form	Basis
First citation of a source, with no full entry anywhere earlier	Full note	CMOS 13.32: short form presupposes a full citation or bibliography entry
Source already cited in full in an earlier note, or listed in a bibliography with full data	Shortened note (surname, short title, page)	CMOS 13.32, 13.33
Same source cited in the next note again	Shortened note; author-only or title-only is allowed, but the fuller form is usually preferred	CMOS 13.37
You are tempted to write “Ibid.”	Use a shortened note instead	CMOS 13.37: ibid. discouraged in the 18th edition

Examples: full note to shortened note

The sources below are invented for illustration and are not real publications. The patterns follow the examples in the Douglas College and University of Portland guides.

Book

Full note: 1. Rosa Delgado, The Quiet Ledger: Accounting Practice in Provincial Libraries (Example University Press, 2019), 41.
Shortened note: 2. Delgado, Quiet Ledger, 58.

The subtitle and the initial “The” are gone; the title is italic.

Journal article

Full note: 3. Tomas Whitfield, “Shelving the Past: Cataloguing Choices in Small Archives,” Journal of Example Studies 12, no. 3 (2020): 77.
Shortened note: 4. Whitfield, “Shelving the Past,” 79.

The title stays in quotation marks, and the journal name, volume and year do not appear.

Chapter in an edited book

For a chapter, the short form uses the chapter author’s surname and a shortened chapter title in quotation marks, in the same pattern as the real example in the University of Portland guide (Just, “Luke 3:1-20,” 57). For an edited work cited as a whole, the University of Portland guide uses the editor’s surname and omits “ed.”

Author-only and title-only notes

Where several successive notes cite one source, CMOS 13.37 lists the author alone or the title alone as options: for example “Delgado, 46.” and then “Quiet Ledger, 46.” The Douglas College guide still treats the fuller author-title form as the usual choice, so keep the short forms for runs where the source is unmistakable.

Worked example: replacing ibid. in a thesis chapter

A chapter written in an older habit might read:

Rosa Delgado, The Quiet Ledger: Accounting Practice in Provincial Libraries (Example University Press, 2019), 41.
Ibid., 44.
Tomas Whitfield, “Shelving the Past: Cataloguing Choices in Small Archives,” Journal of Example Studies 12, no. 3 (2020): 77.
Ibid., 79.
Delgado, Quiet Ledger, 52.

In the 18th-edition form, notes 2 and 4 become shortened notes and note 1 and 3 stay as they are:

Rosa Delgado, The Quiet Ledger: Accounting Practice in Provincial Libraries (Example University Press, 2019), 41.
Delgado, Quiet Ledger, 44.
Tomas Whitfield, “Shelving the Past: Cataloguing Choices in Small Archives,” Journal of Example Studies 12, no. 3 (2020): 77.
Whitfield, “Shelving the Past,” 79.
Delgado, Quiet Ledger, 52.

Every note now stands on its own. Per the Douglas College guide, “ibid.” can obscure the identity of a source, and because shortened citations are usually under one line it saves no space.

In-text citation version

Shortened notes belong to Chicago’s notes-bibliography system: the superscript number in the text points to a footnote whose first citation is full and whose later citations are shortened. Chicago’s separate author-date system does not use footnotes, so this note format does not apply to it. In a thesis, check each shortened note against your bibliography: the surname and short title should let a reader find the matching entry at once (CMOS 13.32). For the bibliography side, see Chicago bibliography and works cited, for the related Turabian pattern, Turabian book citation, and for quotations that run long enough to need their own block, block quotes in Chicago style.

Common errors

Using “ibid.” out of habit. The 18th edition discourages it and recommends shortened citations (CMOS 13.37).
Keeping the subtitle. The short form uses the main title only (CMOS 13.33).
Carrying over publisher and year. The three-part pattern is surname, short title, page; the publication details live in the full note and bibliography.
Cutting a title that is already short. The University of Portland guide shortens only titles of four or more words; a shorter title is repeated whole.
Losing italics or quotation marks. The shortened title is formatted exactly like the full title.
Shortening the same title two different ways. Because the short form must lead the reader to the full entry (CMOS 13.32), choose one short title per source and keep it for the whole thesis.
Writing “ed.” after an editor’s surname. The University of Portland guide omits it in the short form.
Following a 17th-edition guide. Check that any library guide you rely on says 18th edition.

Style-guide edition

This page follows The Chicago Manual of Style, 18th edition (2024). The shortened-note rules were checked against the Douglas College Library and University of Portland library guides on 2026-10-29, and the shortened-note options in 13.37 against the manual’s “what’s new” page (see Sources).

FAQ

What is an abbreviated footnote in Chicago style?

It is the shortened note used for later citations of a source already cited in full: author’s surname, shortened title, page number (CMOS 13.32, 13.33).

Can I still use “ibid.” in Chicago 18?

The manual discourages it and recommends shortened notes (13.37; Douglas College and University of Portland guides). If a supervisor or publisher asks for it, follow their instruction; otherwise use shortened notes throughout.

How many words should the shortened title have?

Two to four keywords from the main title, dropping an initial A, An or The and any subtitle (University of Portland guide). Titles shorter than about four words are left whole.

Can a successive note give only the author or only the title?

Yes. CMOS 13.37 lists author-only and title-only notes as options to avoid repetition, though the fuller author-title form is usually preferred.

Sources

Douglas College Library, “Chicago (18th ed.) Citation Style Guide: Shortened citations,” page last updated October 13, 2026; checked 2026-10-29. https://guides.douglascollege.ca/Chicago18/ShortenedCitations
University of Portland library guide, “Chicago Style, 18th ed.: Short form,” page last updated October 20, 2026; checked 2026-10-29. https://libguides.up.edu/chicago/short_form
The Chicago Manual of Style Online, “What’s new in the 18th edition,” checked 2026-10-29. https://www.chicagomanualofstyle.org/help-tools/what-s-new.html