Library of Congress Classification Class Q (Science)

Overview

The Library of Congress Classification (LCC) system is the primary scheme for organizing collections in many academic and research libraries in the United States and worldwide. Class Q is dedicated to the broad field of Science. It covers the natural and applied sciences, ranging from mathematics to biology, chemistry, physics, earth sciences, and interdisciplinary topics such as environmental science and scientific methodology.

Each subclass within Class Q is identified by a combination of letters and numbers. The letter portion identifies the broad discipline, while the numbers provide a finer granularity, allowing librarians to place a work on a precise shelf location.

Structure of Class Q

Class Q is divided into a series of subclasses, each dealing with a distinct branch of science. The main breakdown is as follows:

• QA Mathematics
• QB Astronomy
• QC Physics
• QD Chemistry
• QE Geology
• QH Natural History & Biology
• QK Botany
• QL Zoology
• QM Human Genetics
• QP Plant Pathology
• QR Microbiology
• R Medicine (included for reference when discussing interdisciplinary science).

Within each subclass, the numerical range further groups topics. For example, in QA (Mathematics), numbers 1999 cover general works, while 10001999 address specific fields such as algebra, analysis, and geometry.

Key Subclasses and Their Numerical Ranges

QA Mathematics

• QA19 General works, history, and philosophy of mathematics.
• QA3039 Logic.
• QA7189 Numbers and numeration.
• QA101199 Algebra.
• QA221229 Geometry.
• QA401459 Calculus and analysis.
• QA640649 Probability and statistics.

QB Astronomy

• QB121 General works, history.
• QB7179 Celestial mechanics.
• QB8189 Observational astronomy.
• QB91979 Specific objects (planets, stars, galaxies).

QC Physics

• QC199 General physics, history, philosophy.
• QC170279 Classical mechanics.
• QC280383 Fluid dynamics.
• QC500595 Thermodynamics.
• QC711739 Optics.
• QC851859 Quantum theory.

QD Chemistry

• QD19 General chemistry, history.
• QD3159 Physical chemistry.
• QD7199 Analytical chemistry.
• QD101199 Organic chemistry.
• QD201299 Inorganic chemistry.
• QD401489 Biochemistry.

QE Geology

• QE19 General works, history.
• QE8085 Mineralogy.
• QE9599 Petrology.
• QE100129 Structural geology.
• QE151185 Paleontology.

QH Natural History & Biology

• QH19 General works, history.
• QH101199 General biology.
• QH301459 Evolutionary biology.
• QH501573 Ecology.
• QH301578 Physiology.

QK Botany

• QK19 General works, history.
• QK5169 Plant physiology.
• QK101669 Systematics and taxonomy.
• QK730744 Economic botany.

QL Zoology

• QL19 General works, history.
• QL101212 Invertebrates.
• QL213279 Vertebrates.
• QL381388 Animal behavior.

QM Human Genetics

• QM19 General works.
• QM370490 Molecular genetics.
• QM500620 Population genetics.

QP Plant Pathology

• QP19 General works.
• QP141569 Diseases of specific plant groups.

QR Microbiology

• QR19 General works.
• QR250491 Bacteriology.
• QR500594 Virology.

How the System Is Used in Libraries

When a new item is acquired, a cataloger examines its subject matter and selects the appropriate LCC call number. The procedure typically follows these steps:

1. Identify the primary discipline (e.g., physics QC).
2. Choose the numeric range that best matches the specific topic (e.g., quantum theory QC851859).
3. Apply cutter numbers (usually based on the author's surname) to create a unique identifier on the shelf.
4. Attach the call number to the items label and enter it into the librarys catalog.

This hierarchical approach enables patrons to browse related works on a shelf and helps librarians maintain order as collections grow.

Further Resources

• Library of Congress Classification Outline (PDF)
• Official LCC website
• OCLC Classify free tool for generating call numbers
• WorldCat explore how other libraries use Class Q