Must FixCitationFound in 5-10% of dissertations

Chicago Citation Format: The Comma Rule Your Committee Will Enforce

Found in 5-10% of dissertations using Chicago style. A missing comma between author and year — (Smith 2020) instead of (Smith, 2020) — marks you as unfamiliar with Chicago author-date format.

FIX

Insert a comma between the author name and year.

What This Issue Is

Chicago Manual of Style (CMOS) author-date format requires a comma between the author name and year in parenthetical citations: (Smith, 2020). This mirrors APA's convention but exists independently in Chicago's system. Omitting the comma — (Smith 2020) — is technically an MLA-style format and signals to your committee that you're mixing up style guides.

Chicago author-date is one of two Chicago citation systems. The other is notes-bibliography (footnotes/endnotes), which is more common in humanities. If your program uses Chicago, confirm with your chair which system you should follow. Author-date is standard in the sciences and social sciences; notes-bibliography is typical in history, literature, and theology programs.

Beyond the basic comma rule, Chicago has its own nuances. Multiple works in one citation are separated by semicolons: (Smith, 2020; Jones, 2019). Multiple works by the same author use just a comma: (Smith, 2019, 2020). Page numbers follow the year with a comma: (Smith, 2020, 45). Each of these punctuation marks matters, and inconsistency will trigger revision requests.

Why Your Committee Flags It

Chicago Author-Date style requires a comma between author and year, similar to APA. Missing punctuation in citations signals carelessness.

Before & After Examples

Before

(Anderson 2022)

After

(Anderson, 2022)

Basic Chicago author-date citation — comma required between author and year.

Before

(Johnson 2021)

After

(Johnson, 2021)

Two-author citation — comma before the year, 'and' between authors (not '&').

Before

(Smith and Wesson 2019)

After

(Smith and Wesson, 2019)

Et al. citation with page number — comma after 'al.' and after year.

Before

(Brown et al. 2022, 45)

After

(Brown et al., 2022, 45)

Self-Check Checklist

Tap each item as you review your chapter.

Related Checks

Should Fix

Ampersand Ban (use "and")

2-4% of dissertations

Must Fix

Et Al. Format

2-3% of dissertations

Should Fix

Number Spelling (0-100)

1-2% of dissertations

Should Fix

Citation Name Consistency

2-5% of dissertations

Must Fix

Citation Format (comma required)

5-10% of dissertations

Frequently Asked Questions

The basic format is (Author, Year): (Smith, 2020). Two authors: (Smith and Jones, 2020). Three or more: (Smith et al., 2020). With page numbers: (Smith, 2020, 45). Multiple sources: (Smith, 2020; Jones, 2019). Always use commas — never ampersands.
No. Chicago always uses 'and' between author names, both in-text and in the reference list. The ampersand is an APA convention. This is one of the key differences to watch for if you're switching from APA to Chicago.
Author-date puts citations in parentheses: (Smith, 2020). Notes-bibliography uses footnotes or endnotes with superscript numbers. Author-date is more common in social sciences. Notes-bibliography is more common in humanities. Your program handbook should specify which to use.
Add the page number after the year, separated by a comma: (Smith, 2020, 45). For a range: (Smith, 2020, 45-52). Unlike MLA, which uses no comma between author and page, Chicago puts commas between every element inside the parentheses.

Sources

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