How to Write Using Chicago Style

Chicago is one of several styles used in professional and academic writing. The guidelines for Chicago style writing are laid out in the Chicago Manual of Style -- most recently in its 16th edition. The manual provides rules for using specific types of punctuation and grammar. In addition, Chicago provides rules for citing and referencing sources used in research. Chicago is most widely used in the fields of the humanities and social sciences, such as art history, american studies, philosophy and religious studies. Many book publishers use it.


The Chicago Manual of Style provides guidelines for the use of punctuation, such as apostrophes, commas and dashes. Many of Chicago's guidelines directly differ from those of other styles, such as AP. For instance, Chicago style uses the serial comma, sometimes known as the Oxford comma. When listing more than two words, phrases or clauses, a comma is placed after the second to last item in the list. The difference in style is shown below:

Without serial comma:

Susie loved arugula, kale and cabbage.

With serial comma:

Susie loved arugula, kale, and cabbage.

In Chicago style, all singular possessive nouns end in an apostrophe and an s ('s) regardless of their last letters or if they are proper nouns. For example:

mistress's ox's Paris's Alex's

Titles and Initials

Chicago also differs from AP in its lack of periods in all two-letter abbreviations and its spacing of initials. In Chicago, two-letter abbreviations do not use periods:

MD, instead of M.D. US Marshall, instead of U.S. Marshall

When abbreviating a name using initials, periods are used, and the initials are separated by a space:

H. L. Mencken W. A. Mozart C. G. Jung, PhD

An exception to this rule occurs when initials are used alone in place of a name:



Chicago's "general rule" recommends spelling out all numbers up to and including 100. In addition, any number between one and 100 that is followed by hundred, thousand, hundred thousand, million, billion, trillion, etc. is spelled out. Any other number is written as numerals. For example:

fifteen, seventy-five, one hundred, 123, thirteen thousand, 98,761, forty-nine billion.

Chicago's "alternative rule" is the same as that used by AP style: Spell out all numbers up to and including nine, and use numerals for the rest. For instance:

five, seven, 14, 16,000, 17,891.

The Chicago manual notes that the alternative rule is usually used in scientific or journalistic contexts.

In Chicago style, a number at the beginning of a sentence is always spelled out, and not a numeral. If this would make a sentence awkward, reword the sentence instead.

Chicago Documentary Note Style

In addition to providing rules for grammatical and punctuation style, the Chicago Manual of Style also provides a set of instructions for citing sources in your paper. Chicago style provides two different formats for citations: documentary note and author-date. Documentary note is used largely in the humanities and arts, while author-date is used in the sciences and social sciences.

Documentary note citation style differs from many other reference styles in that it uses footnotes or endnotes in place of in-text parenthetical citations. When you reference or quote a source in your paper, provide a footnote or endnote giving the information of that source.

The first footnote or endnote citation for a source should include the author's name, the source title, publisher's information and year of publication, as well as the page number of the cited information. Any further footnotes or endnotes for the same source only need the author's last name, source title and page number. If the same source is cited multiple times in a row, then each source past the first uses "Ibid." instead of the author's name and title. Footnotes and endnotes are single-spaced.

Documentary note style also requires a bibliography page or pages to be included after the body of the paper. The bibliography is an alphabetical list of all sources referenced in the paper.

Author-Date Style

Author-date citation style has more in common with other reference styles, such as the those of the American Psychological Association and the Modern Language Association. In-text citations in author-date style include the author of the work referenced and the year of its publication. If the work is directly quoted, a page number is included as well.

Author-date style also includes a reference page after the last page of a paper. Like a documentary note style bibliography, this is an alphabetized list of sources including titles and publisher information. However, the information in author-date style is formatted in a different order: the author's name, followed by the year, work title and publication information.

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