Editing Dewey Decimal Classification (section)

==Design==
The Dewey Decimal Classification organizes library materials by discipline or field of study. The scheme comprises [[List of Dewey Decimal classes|ten classes]], each divided into ten divisions, each having ten sections. The system's notation uses Indo-Arabic numbers, with three whole numbers making up the main classes and sub-classes and decimals designating further divisions. The classification structure is [[hierarchical]] and the notation follows the same hierarchy. Libraries not needing the full level of detail of the classification can trim right-most decimal digits from the class number to obtain more general classifications.<ref>{{harvp|Chan|2007|pp=326–33}}1</ref> For example:

:500 Natural sciences and mathematics
:: 510 Mathematics
::: 516 Geometry
:::: 516.3 Analytic geometries
::::: 516.37 Metric differential geometries
:::::: 516.375 Finsler geometry

The classification was originally enumerative, meaning that it listed all of the classes explicitly in the schedules. Over time it added some aspects of a [[faceted classification]] scheme, allowing classifiers to construct a number by combining a class number for a topic with an entry from a separate table. Tables cover commonly used elements such as geographical and temporal aspects, language, and bibliographic forms. For example, a class number could be constructed using 330 for economics +&nbsp;.9 for geographic treatment +&nbsp;.04 for Europe to create the class 330.94 European economy. Or one could combine the class 973 (for the United States) +&nbsp;.05 (for [[periodical]] publications on the topic) to arrive at the number 973.05 for periodicals concerning the United States generally. The classification also makes use of mnemonics in some areas, such that the number 5 represents the country Italy in classification numbers like 945 (history of Italy), 450 (Italian language), and 195 (Italian philosophy). The combination of faceting and mnemonics makes the classification ''synthetic'' in nature, with meaning built into parts of the classification number.<ref>{{harvp|Chan|2007|p=331}}</ref>

The Dewey Decimal Classification has a number for all subjects, including fiction, although many libraries maintain a separate fiction section shelved by alphabetical order of the author's surname.  Each assigned number consists of two parts: a class number (from the Dewey system) and a book number, which "prevents confusion of different books on the same subject".<ref name="DDC1876" /> A common form of the book number is called a [[Cutter number]], which represents the author.<ref>{{harvp|Chan|2007|pp=333-362}}</ref>

===Classes===
{{Main|List of Dewey Decimal classes}}
(From DDC 23<ref name=DDC23intro>{{cite web | title = Introduction to the Dewey Decimal Classification | author = OCLC | url = https://www.oclc.org/dewey/versions/print.en.html | access-date = 8 December 2013 | archive-date = December 12, 2013 | archive-url = https://web.archive.org/web/20131212235819/https://www.oclc.org/dewey/versions/print.en.html | url-status = live }}</ref>)
* [[List of Dewey Decimal classes#Class 000 &ndash; Computer science, information and general works|000]] – Computer science, information and general works
* [[List of Dewey Decimal classes#Class 100 &ndash; Philosophy and psychology|100]] – Philosophy and psychology
* [[List of Dewey Decimal classes#Class 200 &ndash; Religion|200]] – Religion
* [[List of Dewey Decimal classes#Class 300 &ndash; Social sciences|300]] – Social sciences
* [[List of Dewey Decimal classes#Class 400 &ndash; Language|400]] – Language
* [[List of Dewey Decimal classes#Class 500 &ndash; Science|500]] – Pure science
* [[List of Dewey Decimal classes#Class 600 &ndash; Technology|600]] – Technology
* [[List of Dewey Decimal classes#Class 700 &ndash; Arts and recreation|700]] – Arts and recreation
* [[List of Dewey Decimal classes#Class 800 &ndash; Literature|800]] – Literature
* [[List of Dewey Decimal classes#Class 900 &ndash; History and geography|900]] – History and geography

===Tables===
(From DDC 23<ref name=DDC23intro/>)
*T1 Standard Subdivisions
*T2 Geographic Areas, Historical Periods, Biography
*T3 Subdivisions for the Arts, for Individual Literatures, for Specific Literary Forms
**T3A Subdivisions for Works by or about Individual Authors
**T3B Subdivisions for Works by or about More than One Author
**T3C Notation to Be Added Where Instructed in Table 3B, 700.4, 791.4, 808–809
*T4 Subdivisions of Individual Languages and Language Families
*T5 Ethnic and National Groups
*T6 Languages

===Relative Index===
<!-- EDITORS: please retain Dewey's original (eccentric) spelling here.  "Relativ" is correct. --><!--The materials from the Dewey organisation itself now spell it "relative". There seems no reason to retain Dewey's eccentric spelling.-->
The Relative Index (or, as Dewey spelled it, "Relativ Index") is an alphabetical index to the classification, for use both by classifiers and by library users when seeking books by topic. The index was "relative" because the index entries pointed to the class numbers, not to the page numbers of the printed classification schedule. In this way, the Dewey Decimal Classification itself had the same relative positioning as the library shelf and could be used either as an entry point to the classification, by catalogers, or as an index to a Dewey-classed library itself.<ref>
{{Citation
        | publisher = Govt. print. off.
        | location = Washington
        | author = United States. Office of Education.
        | title = Public libraries in the United States of America
        | date = 1876
        | page = 628    
        | ol = 23403373M
 }}
</ref>