The Chicago Manual of Style presents two basic documentation systems, the humanities style (notes and bibliography) and the author-date system. Choosing between the two often depends on subject matter and nature of sources cited, as each system is favored by different groups of scholars.
The humanities style is preferred by many in literature, history, and the arts. This style presents bibliographic information in notes and, often, a bibliography. It accommodates a variety of sources, including esoteric ones less appropriate to the author-date system.
The more concise author-date system has long been used by those in the physical, natural, and social sciences. In this system, sources are briefly cited in the text, usually in parentheses, by author's last name and date of publication. The short citations are amplified in a list of references, where full bibliographic information is provided.
The University of Chicago Press
Note: Examples in this guide are for the humanities style (i.e. notes and bibliography) of CMOS. For author-date system examples, please use the manual.
A Manual for Writers of Research Papers, Theses, and Dissertations (published by the University of Chicago Press and often referred to simply as Turabian), is a style guide for writing and formatting research papers (such as the arrangement and punctuation of footnotes and bibliographies). The style described in this book is commonly known as Turabian style, after the book's original author, Kate L. Turabian.
Wikipedia contributors. "A Manual for Writers of Research Papers, Theses, and Dissertations." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 3 Jan. 2016. Web. 4 Feb. 2016.
The Chicago and Turabian styles are nearly identical.
Kate Turabian, the dissertation secretary at the University of Chicago for over 30 years, developed her guide for students and researchers writing papers, theses, and dissertations. Her manual is based on the University of Chicago Press's Manual of Style and departs from it in few places. "Turabian," as her guide is called, synthesizes the rules most important for students' papers and other scholarly research not intended for publication, and omits some of the publishing details and options that "Chicago" provides.