Hey man, can you explain what the decimals in the system mean? I get that 001-099 and so on are specifics, but what do the .# mean?
The Dewey Decimal Classification system allows every non-fiction topic to be categorized under one of ten broad subjects, each starting with a different digit (see my pinned post).
Say you were looking for a book about narwhals
5XX: science 59X: zoology 599: mammals 599.5: cetacea and sirenia (aquatic mammals) 599.54: other toothed whales (most whales are under 599.52, and dolphins are under 599.53, while 599.55 is about manatees and dugongs) 599.543: narwhals
Every digit after the decimal point represents a subcategory of the previous. The more digits you add, the more specific the classification. It's turtles all the way down; some subjects are so dense that you need long strings of digits to find exactly what you're looking for. Softball is under 796.3578. Mayan folklore is under 398.2097281. The Beatles are under 782.4216609; that's the exact same number of digits as Mayan folklore, so you'd think they'd have the subcategory all to themselves, but no, they share it with a ton of other bands because it actually represents the broad topic "history, geographic treatment, and biography of specific rock songs."
Not every single subject gets that granular. In fact, most require less than six digits total because there aren't going to be that many books on any given subject to warrant that level of specificity. 551.312 represents everything to do with glaciers; whether they're from Norway or Antarctica (complete opposite sides of the globe), they share the same six digits. There's really no need for more.
But just because a topic exists doesn't necessarily mean your library will carry books about it; mine, for example, has several non-fiction books about platypuses (599.29) but none about possums (599.23). Damn shame.
Feel free to submit any posts you want me to classify, or shoot me an ask if you have a specific topic in mind.

















