NLM Classification Fundamentals

Classification (Class) Numbers

Classification Notes

Captions

Captions describe the classification number. It may or may not be a MeSH term. You can check if the caption is a MeSH term by using the MeSH Browser.

Example

In the Optometry section, "Optometry," "Eyeglasses," "Contact lenses" are MeSH Terms. "Ocular prothesis" is not but using the MeSH Browser, you can see it is an entry term for "Eye, Artificial."

Example of several MeSH terms in Captions
Class Number	Caption
WW Ophthalmology Optometry
WW 350	Optometry
[WW 352]	[This number not used]
WW 354	Eyeglasses
WW 355	Contact lenses
WW 358	Ocular prosthesis

Period

A period (".") is used to separate related but different concepts within the same caption.

Example

WA 356 includes the separate, but related, concepts of "Elder welfare" and "Elder abuse."

Example of periods in Captions
Class Number	Caption
WA Public Health Health Issues of Specific Groups of People
WA 356	Elder welfare. Elder abuse
WA 360	Military health. Veterans health
WA 370	Persons with disabilities

Cutter

Named after Charles A. Cutter, the "Cutter number" is a combination of letters and numbers that generally form an alphabetical arrangement representing the author’s name or the title of the work following the classification number on the bibliographic record. If needed, there will be instructions for assigning cutter information for names in the class notes. (Note: Cutter alphanumeric codes may also be used to alphabetically arrange geographic notations. See discussion under Table G/Geographic Notation section.)

Example

Note the cutter information for WZ 28 in the class notes.

Example of Cutter
Class Number	Caption
WZ History of Medicine. Medical Miscellany Reference Works. General Works
WZ 28	Individual museums, exhibitions, etc. (Cutter from name of museum) (Table-G)

Note about the LCC

When using a Library of Congress class number subdivided by geographic or A–Z topic, the appropriate cutter should be included in the NLM class number. Geographic cutters should be taken from the Library of Congress Classification and Shelflisting Manual "Section G300 Regions and Countries Table." If a double LC author cutter is present, NLM does not use the second cutter in the classification number.

Explanatory

Some notes include more explanation about the class number. It helps define what is classed at a particular number or elsewhere.

Example

Note the explanatory description for "Heavy metals and their compounds" in smaller font.

Example of Explanatory Description
Class Number	Caption
QV Pharmacology Heavy Metals
QV 290	Heavy metals and their compounds (General or not elsewhere classified) Include works on rare earth metals not indexed elsewhere. Classify works on toxicological effects of all metals here also. Classify here works on chelating agents in general, but classify works on particular chelating agents with specific metal.