Handling Discontinued Entries in DDC with Notes

Knowledge does not sit still, and neither does the system used to organise it. The Dewey Decimal Classification (DDC) is revised continuously, which means some numbers that were once perfectly valid eventually fall out of use. When that happens, the number does not simply vanish. It stays printed in the schedules inside square brackets, accompanied by a short note that tells the classifier exactly what to do instead. These small notes under bracketed entries are easy to overlook, yet they protect a library’s catalogue from drifting into inconsistency. This post explains why numbers get discontinued, what the notes under these bracketed entries mean, and how to read them correctly during everyday classification work.

What a discontinued entry actually is 🔗

In DDC terminology, discontinuation means shifting a topic, or the entire contents of a number, to a more general number within the same hierarchy, or removing the topic altogether. The defining feature is that the topic usually moves “upward” to its superordinate (broader) number rather than sideways to an unrelated one. The publisher, OCLC, defines it as the shifting of a topic or the entire contents of a number to a more general number in the same hierarchy, or the complete removal of the topic or number.

When a topic is discontinued, its old number is enclosed in square brackets. According to the official introduction to the scheme, numbers in square brackets represent topics that have been relocated or discontinued, or are unassigned, and numbers in square brackets are never used. This last point is the rule that matters most in practice. A bracketed number is a signpost, not a destination. You read it, follow the note attached to it, and assign the new number it points to.

Why numbers get discontinued 🔗

Classification mirrors the literature it organises. As subjects grow, merge, or fade, the structure has to adjust. The DDC recognises two main reasons for discontinuing a number.

The literature has become too thin 🔗

A number exists to gather books on a topic. If almost nothing is being published on that topic any longer, keeping a separate number creates more clutter than clarity. In this situation the topic is folded back into a broader number that can comfortably hold the few works that exist. OCLC explains that a topic is discontinued because it either has a negligible current literature or represents a distinction that is no longer valid in the literature or common perception of the field.

The distinction no longer makes sense 🔗

Sometimes a topic was once treated as separate but is no longer seen that way by scholars in the field. The boundary between two ideas may dissolve, or a term may simply go out of fashion. When the distinction that justified a separate number disappears, the number is discontinued and its contents merge with the broader class. This keeps the schedule aligned with how people actually think about the subject today.

It is worth remembering that change inside a single edition is normal. The Dewey editorial team notes that an existing number can be deleted within one edition when all of its topics are discontinued or relocated, which is exactly why classifiers are advised to check the current version of the schedule rather than relying on memory.

How discontinued entries appear in the schedules 🔗

Open any printed DDC schedule and you will occasionally see a number sitting inside square brackets with a heading and a short instruction beneath it. The brackets are the visual cue. They tell you immediately that this number is no longer live. The deprecated number carries a note indicating when the change occurred, and that date helps you trace where the topic went. The note is the working part of the entry. Without it, a bracketed number would only tell you that something has changed, not what to do about it.

Types of notes found under discontinued entries 🔗

Two kinds of instructions do most of the work under bracketed entries. Recognising the difference helps you respond correctly rather than guessing.

“Do not use” notes 🔗

A do-not-use note is a direct instruction telling the classifier not to use a number, or part of a number, and to use something else instead. These notes commonly appear with bracketed standard subdivisions. As the official introduction puts it, do-not-use notes instruct the classifier not to use all or part of the regular standard subdivision notation, but instead to use a special provision or standard subdivision notation at a broader number. The note removes any ambiguity. It blocks the bracketed number and redirects you in the same breath.

“Class in…” notes 🔗

The class in note is the redirection itself. It names the number where the topic now belongs. When a number is discontinued, the note under the bracketed entry typically reads “class in” followed by the broader number that has absorbed the topic. OCLC confirms that notes at both ends of the discontinuation identify the old and new locations. So the bracketed entry tells you where the topic used to live, and the “class in” note tells you where to send it now.

Notes at the receiving number 🔗

Discontinuation leaves a trail at both ends, not just at the old number. The broader number that now holds the topic may carry its own note acknowledging the change, and from 2017 onward many of these appear in a history box within the electronic version of the scheme. This two-sided record is useful when you are reclassifying older stock, because it lets you confirm that the move was intentional rather than an error in an older catalogue record.

A worked example: educational sociology and 370.19 🔗

A familiar textbook illustration is the entry for educational sociology. The topic of educational sociology is handled at 370.19, the number for the sociology of education within the education class. A bracketed entry for the topic therefore carries a note reading “educational sociology, class in 370.19”, steering the classifier to that number rather than the older or alternative location.

You can see the effect of this convention in working catalogues. Libraries routinely assign books on the sociology of education to 370.19, and records for titles dealing with the sociological analysis of education are catalogued at 370.19 in Indian academic libraries. The instruction does its job quietly: a cataloguer who lands on the bracketed number is told, in a few words, to use 370.19 and move on. The result is that every book on the topic ends up shelved together, regardless of which older number a previous edition might have suggested.

Discontinuation is not the same as relocation 🔗

Students often blur discontinuation and relocation, but the DDC treats them as distinct. Relocation is the shifting of a topic from one number to another number that differs from the old number in respects other than length. In other words, relocation can move a topic sideways to an unrelated part of the scheme. Discontinuation, by contrast, generally moves a topic up to its broader parent number, or removes it entirely.

The practical clue is the note. A discontinued entry usually pushes you to a shorter, more general number in the same chain, while a relocation may send you somewhere structurally different. The official documentation groups both under the same housekeeping process and provides dedicated relocation and discontinuation notes so that classifiers can follow either kind of change without confusion. Reading the note carefully, rather than assuming, is what keeps the two apart.

Why these small notes matter so much 🔗

Notes carry information that the notation and heading alone cannot express. The introduction to the scheme stresses that notes are important because they supply information that is not obvious in the notational hierarchy or in the heading regarding order, structure, and subordination. For discontinued entries, this is the whole point. The bracketed number looks like a usable class until the note reveals that it is not.

Ignoring these notes has a real cost. If a classifier uses a bracketed number, books on the same subject end up split across an old number and a current one, and a reader browsing the shelves or the catalogue may never find half of them. Following the “do not use” and “class in” notes keeps related material together and keeps the catalogue consistent across the years and editions a collection passes through. For libraries that hold older as well as newer editions of the scheme, these notes are the bridge that keeps the whole collection speaking the same classification language.

A simple working habit covers most situations. When you reach a number in square brackets, stop, read the note attached to it, and assign the number that the note points to. Never assign the bracketed number itself. That one rule, applied consistently, turns discontinued entries from a source of confusion into a reliable set of road signs.

What do you think? When you come across a bracketed number in the schedules, do you pause to read the note, or is it tempting to use the number as printed? And in a library that holds books classified under several past editions, how would you decide whether to reclassify older titles into their current discontinued-entry destinations?

References

1. https://ddc.typepad.com/025431/2016/03/answers-to-questions.html
2. https://www.oclc.org/content/dam/oclc/dewey/resources/summaries/deweysummaries.pdf
3. https://help.oclc.org/Librarian_Toolbox/OCLC_glossaries/Dewey_Decimal_Classification_glossary
4. https://socialsci.libretexts.org/Courses/Sacramento_City_College/LIBT331:_Library_Cataloging_Procedures_(Li)/01:_Cataloging_Rules_and_Tools/1.04:_Classification_systems_-_Library_of_Congress/1.4.03:_Introduction_to_the_Dewey_Decimal_Classification
5. https://opac.nls.ac.in/bib/13556
6. https://www.oclc.org/content/dam/oclc/webdewey/help/relocations-discontinuations1.pdf
7. https://www.oclc.org/content/dam/oclc/dewey/versions/print/intro.pdf