A segmentation mark is used to indicate the end of an Abridged Edition 15 (A15) number within a DDC 23 number. If the A15 number and the DDC 23 number are the same, no segmentation mark is given.
The Dewey Program uses a slash in the 082 MARC field to indicate where to segment:
082 00 ‡a 940.3/2252 ‡2 23
The prime mark is used for segmentation in DDC numbers when Cataloging in Publication Program data are printed in the book:
Dewey numbers generally will not contain segmentation if they were imported into the Library of Congress catalog via the copy cataloging work stream.
Prior to Edition 22, the rules called for a segmentation mark at the start of every standard subdivision (notation from Table 1) as well as at the end of the abridged number. For example, 551.21/09797/84 includes a segmentation slash before the zero that marks the start of the standard subdivision T1—09 and a second slash at the end of the abridged number. The same number assigned after the segmentation rules changed, would be 551.210979/84 to show where the abridged number ends.