Latin America and Caribbean

Segmentation Marks in Dewey Numbers

The Decimal Classification Division (DCD) of the Library of Congress has decided to discontinue the practice of assigning segmentation marks (also referred to as prime marks or slash marks) to indicate the beginning of standard subdivisions in DDC numbers.

For more information see: 025.431: The Dewey blog; Sweet segment solution.


The Library of Congress Decimal Classification Division, along with the Dewey editorial team, is considering a change in segmentation practice. The segmentation marks in Dewey numbers currently show the end of an abridged number or the beginning of a standard subdivision. For example:

155.6/6 The slash shows the end of the number for the same topic in the abridged edition, 155.6

809/.89287 The slash shows the end of the number for the same topic in the abridged edition, 809

324.6/23/0973 The first slash shows the end of the abridged number (324.6); the second slash shows the beginning of the standard subdivision (0973)

282/.092/2 The first slash shows the beginning of the standard subdivision (0922); the second slash shows the end of the abridged number (the standard subdivision 0922 is shortened to 092 in the abridged edition)

We are considering simplifying our segmentation service to include a single mark that shows the end of the abridged number: 155.6/6, 809/.89287, 324.6/230973, 282.092/2. We would like to hear from the library and library vendor community about your current use of segmentation marks, and the impact a change in policy would have on that use. Please send your comments, along with your name and affiliation by June 15 to Dennis McGovern (dmcg@loc.gov), Chief, Decimal Classification Division, Library of Congress.

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