Dewey Decimal Classification

The third summary contains the thousand sections. The third digit in each three-digit number indicates the section. Thus, 610 is used for general works on medicine and health, 611 for human anatomy, 612 for human physiology, 613 for personal health and safety. Arabic numerals are used to represent each class in the DDC. A decimal point follows the third digit in a class number, after which division by ten continues to the specific degree of classification needed. A subject may appear in more than one discipline. For example, “clothing” has aspects that fall under several disciplines. The psychological influence of clothing belongs in 155.95 as part of the discipline of psychology; customs associated with clothing belong in 391 as part of the discipline of customs; and clothing in the sense of fashion design belongs in 746.92 as part of the discipline of the arts. Hierarchy Hierarchy in the DDC is expressed through structure and notation. Structural hierarchy means that all topics (aside from the ten main classes) are part of all the broader topics above them. Any note regarding the nature of a class holds true for all the subordinate classes, including logically subordinate topics classed at coordinate numbers. Notational hierarchy is expressed by length of notation. Numbers at any given level are usually subordinate to a class whose notation is one digit shorter; coordinate with a class whose notation has the same number of significant digits; and superordinate to a class with numbers one or more digits longer. The underlined digits in the following example demonstrate this notational hierarchy: 600 Technology Agriculture and related technologies 630 636 Animal husbandry Dogs 636.7 636.8 Cats represents, and often one or more notes. All entries (numbers, headings, and notes) should be read in the context of the hierarchy. In the print version of the DDC, the first three digits of schedule numbers (main classes, divisions, sections) appear only once in the number column, when first used. They are repeated at the top of each page where their subdivisions continue. Subordinate numbers appear in the number column, beginning with a decimal point, with the initial three digits understood. Some numbers in the schedules and tables are enclosed in parentheses or square brackets. Numbers and notes in parentheses provide options to standard practice. Numbers in square brackets represent topics that have been relocated or discontinued, or are unassigned. Square brackets are also used for standard subdivision concepts that are represented in another location. Numbers in square brackets are never used. Number Building Only a fraction of potential DDC numbers are included in the schedules. It is often necessary to build or synthesize a number that is not specifically listed in the schedules. Such built numbers allow for greater depth of content analysis. There are four sources of notation for building numbers: (A) Table 1 Standard Subdivisions; (B) Tables 2–6; (C) other parts of the schedules; and (D) add tables in the schedules. Number building is initiated only upon instructions in the schedules (except for the addition of standard subdivisions, which may take place anywhere unless there is an instruction to the contrary). Number building begins with a base number (always stated in the instruction note) to which another number is added. More Information The Dewey web site (www.oclc.org/dewey) contains up-to-date information about the DDC, DDC products and services, and DDC licensing. For more information about the structure and application of the Dewey Decimal Classification, consult the Introduction. A more in-depth introduction to the Dewey Decimal Classification may be found on the Dewey Teaching Site at Second Summary Hundred Divisions 000 010 020 030 040 050 060 070 080 090 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 410 420 430 440 450 460 470 480 490