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Library & Research Jargon: Library of Congress

A dictionary-guide to those weird jargon words and phrases we librarians and your professors sometimes use.

Library of Congress Classification

The Library of Congress Classification system (LCC) is the system that academic libraries generally use to classify and organize their materials. The cataloged materials are assigned a subject heading and call number, along with the title, author, etc. This allows materials to be organized and shelved in a consistent manner.

Call Numbers

A call number is the mark on the spine of a library book or item, which is also listed in the library catalog to indicate the item’s location in the library. With the LCC system, each book has a unique call number which is a combination of letters and numbers. The call number can have anywhere between three and seven lines, which all indicate a different part of the book’s identity.

Example: PR 6068.O93 H337 1999breakdown of elements of a call number on a library book

  1. Classification
    • PR = British literature
  2. Subclass (sometimes the subject heading)
    • 6068 = collections of general literature
  3. Cutter number: author
    •  .O93 = J.K. Rowling
  4. Cutter number: title or series
    • H337 = Harry Potter series
  5. Publication year (or sometimes the copyright date)
    • 1999 (Sorcerer's Stone's publication year)
  6. Copy number (If there are multiple copies of the same item in the library, they will often have copy numbers assigned to them, so they might have c.1 and c.2 at the end of the call number.)

Don’t worry— you don’t need to know what all these numbers and letters mean! It might be useful to know the general subject and subclass of the topics you’ll be researching for your major (ex: RT=nursing, PS=American literature), but the catalog will always tell you where to go.

Subject Headings

A subject heading is a word or phrase assigned to a book or other material by the LOC so that it can be classified and retrieved by that subject. Subject headings are usually nouns, like “schools”, “nuclear physics”, “local taxation”, etc. LOC subject headings can also be more detailed and specific by being inverted with a comma to add an adjective to the noun, or by using dashes to add subdivisions (subcategories). A book can have more than one subject heading; sometimes they have several.


Vehicles, Land

United States—Armed Forces

Great Britain—History—William I, 1066–1087

Technology—History—20th century

Art, Chinese—To 221 B.C.

Classification Outline

A — General works
B — Philosophy. Psychology. Religion
C — Auxiliary sciences of history
D — World history and history of Europe, Asia, Africa, Australia, New Zealand, etc.
E — History of the Americas
F — History of the Americas
G — Geography. Anthropology. Recreation
H — Social sciences
J — Political science
K — Law
L — Education
M — Music and books on music
N — Fine arts
P — Language and literature
Q — Science
R — Medicine
S — Agriculture
T — Technology
U — Military science
V — Naval science
Z — Bibliography. Library science. Information resources (general)