Chicago Style has two referencing style systems – the Notes/bibliography style system (also known as "Humanities style") and the Author/date style system (also known as "Scientific/ Social Sciences style'). This guide covers the Notes/bibliography style system, which uses notes (either footnotes or endnotes) and a bibliography at the end of the paper. It is used most commonly in the humanities.
It is recommended, but not absolutely required, that you cite your sources in both notes and a bibliography. If you are considering not providing a bibliography, we suggest that you consult your instructor first since it is still standard practice to include both notes and a bibliography. (14.14)
Double space the main body of the essay. Entries in the bibliography and endnotes are single spaced within entries, but double-spaced between entries (unless your instructor prefers double-spacing throughout).
Footnote form and bibliographic form differ slightly. The headings on the left-hand side of this guide indicate bibliographic and footnote form; they are not part of the entry.
Notes can be either footnotes (placed at the bottom of the same page as the referenced text) or endnotes (listed on a separate sheet at the end of the essay). Footnotes and Endnotes are structured in exactly the same way.
When citing a source, insert a superscript (raised) number within the text. Use normal full sized font numbers for note reference numbers in the notes themselves. The notes are numbered consecutively throughout the paper. Most word processing programs handle footnotes automatically. (14.19)
1. Terrence Deacon, Incomplete Nature: How Mind Emerged from Matter
(New York: W.W.Norton, 2012), 68.
The first time you cite a source in a footnote or endnote, you give a complete citation. If you refer to the same source again, you may use a shortened form for notes (including an abbreviated form of the title). (14.24)
2. Deacon, Incomplete Nature, 76.
If you cite the same source two or more times in a row, instead of the author’s last name and the abbreviated title, use Ibid. If the reference is the same, but the page number is not, add the page number to Ibid. (14.29)
3. Ibid., 83.
The bibliography is arranged alphabetically by the author’s last name or by the title if there is no author. (14.57)