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Introduction: Do You Know Your Dewey?

I have a confession to make. I’ve worked in libraries in some capacity for over ten years now, but apart from a superficial knowledge of the topic, I don’t really know my Dewey Decimal System. Sure, I can tell you that true crime is 364 or that test prep is 373, but if you were to ask me about lighthouses (387.1), dogs and cats (636.7-636.8), or the moon (523.3) I’d be stumped. In our modern era of computers, it’s generally assumed that we don’t really need to know our Dewey classifications, since we can look up anything we want with just a few clicks. But, as I realized one morning when the catalog was down, a basic understanding of Dewey is not only helpful, but necessary.

So, I’ve decided to take a journey through the entire DDS (Dewey Decimal System). And I hope that you’ll join me along the way. Over the course of the next few weeks, we’ll explore all the way from 001 (Knowledge) to 999.9 (Extraterrestrial Regions). And it’s going to be a wild ride!

A few quick notes before we begin. Westlake Porter Public Library is a popular materials library. This means that there are certain areas of the DDS that might not be included in our collection, as they’re too specialized (or even too obscure) to circulate. On a separate note, there are some areas of the DDS that aren’t being used anymore anywhere or were never used at all. For our purposes, I’ll refer to these areas using the official term of “unassigned”. If an unassigned call number was used at one point, I’ll try to find out what it was and to share that information with you. Of course, if it was never used, I’ll let you know that, too!

Getting Our Terms Straight

There are 10 main divisions of Dewey (000, 100, 200, 300, 400…etc.) up to 900. These are called Classifications or Classes. We’ll use both terms interchangeably here.

Also, there are a few different abbreviations that I’ll use throughout these posts: DDS (Dewey Decimal System) and MDS (Melville Dewey System) both refer to the classification system itself (and while I prefer MDS, I’ll use both). DDC (Dewey Decimal Classification) refers to the physical resource that I’m using to learn about each classification. This resource comes in four thick volumes and is mostly used by catalogers (I’m borrowing it from one of ours!) If you’d like to follow along, but can’t get your hands on a copy of the DDC, you can also try using MDS from LibraryThing. This is a free, interactive, easy to use resource for cataloging your personal collection at home (or for exploring the depths of the MDS).

You’re looking at about 2,600 pages here, and that’s only half the set!

Addressing Concerns

Personally, I’m a big fan of the MDS. But, I’ll be the first to agree that there are some prickly issues with the system. For example, you’ll find books on very similar topics spread all throughout the library. For example, 040 contains collected essays and anthologies, but you can also find these sorts of books in the 800s. Or, a book about President Obama can be found in the 320s (if we’re talking about his politics), the 920s (if we’re looking for a biography), or the 970s (for his historical contributions).

Another common complaint against MDS is that the system clearly skews towards Western and Christian topics. For example, most of the 200s (religion) are dedicated to Christianity (220-289), while 290 is considered a catch-all of sorts, covering “other” religions (ie. anything from Judaism in 296 to Voodoo in 299.675; 297, for example, covers Islam, Bábism, and Baha’i!). Likewise, in the 400s, the 490s are dedicated to “other languages” that don’t fall into the categories of English, German, French, Italian, Spanish, Latin, or Greek; 890 is Literature of Other Countries, and 990 is Oceania and Elsewhere, which covers everything from Australia to outer space!

But the Good Stuff?

But, there’s still a lot of great stuff about MDS. The system is constantly evolving to adapt to new topics that Dewey himself could only have dreamed of, such as Artificial Intelligence. And many of those “unassigned” classifications that I mentioned earlier can be used for adding in these additional topics as they arise. Since the general classifications are just that, general, there’s plenty of room for growth.

Another plus is the nesting system used for classifications. While some might find it complicated, I love that it allows you to get as specific as you’d like. For example, if I wanted to read about the lives of soldiers in the Civil War, I’d be able to find it:

  • 900 History and Geography
    • 970 North America
      • 973 United States
        • 973.7 Administration of Abraham Lincoln, 1861-65 Civil War
          • 973.78 Personal Narratives
            • 973.783 Army Life

Pretty cool, right?

How This Works

I plan on covering one classification of Dewey each week, so we should be done with the entire project in about three months:

  • 000- General Works
  • 100- Philosophy
  • 200- Religion
  • 300-Social Sciences
  • 400-Language
  • 500- Science
  • 600- Technology
  • 700- The Arts
  • 800- Literature
  • 900- History and Geography

So, keep an eye on our blogs for more updates. I’ll start with our first classification, 000 (Knowledge) next week! I look forward to exploring the library with you!


I'm the Reader's Advisory Librarian at WPPL. My interests include old horror films, classic novels, manga and anime, paper-crafting, and plants. If you like my suggestions, you can request personalized recommendations from me on My Librarian page.