Like Library of Congress call numbers, Dewey Decimal call numbers group books together by broad topic or classification (number before the decimal), and then use further letters and numbers to group books into more specific topics and subtopics (letters and numbers after the decimal).

While the call numbers appear horizontally in the online catalog, they will appear vertically on the spine or edge of the book.

For example, to read the Dewey Decimal call number in the catalog: **630.51 ****P884**

**630.51: **The number in front of the decimal is read as a whole number (six hundred and thirty), then treat the rest as a decimal. 630.51 would come between 630.5 and 630.52.

**P884: **For the final number, go to the letter first and then read the rest as the whole number. P884 would come between P883 and P885.

*Example taken from the U. of Chicago libraries.*

The call number appears horizontally on the spine:

* *