H 80 Order of Subject Headings
BACKGROUND: Both the Library of Congress classification number and the first subject heading(s) assigned to a work are based on the predominant topic of the work. Therefore the class number and the first subject heading(s) usually match. However, it is not always possible to achieve an exact match because the classification system and the subject headings system have different conventions. Class numbers, for example, are sometimes less specific and sometimes more specific than subject headings. In some cases, it requires several subject headings collectively to designate what the classification expresses in a single caption. Therefore the principle that the first subject heading(s) matches the class number is a somewhat flexible one. This instruction sheet provides guidelines for the order of the subject headings assigned to a particular work.
Note: The Library of Congress does not apply the provision of the MARC 21 Format for Bibliographic Data that allows indication of primary and secondary descriptors in the first indicator of 650 fields.
1. General rule. Assign the heading that represents the predominant topic of the work as the first subject heading. If the predominant topic cannot be represented by a single heading, assign as the first and second headings the two headings that, taken together, express the predominant topic. Although it is not significant which of the two is assigned first and which second, if one of the two more closely approximates the class number it is usually assigned first.
For works of individual biography, assign as the first subject heading the name of the biographee.
2. Works with two equally important topics. If a work has two equally important major topics, assign heading(s) for the second of these topics immediately after the heading(s) for the first, and before any headings for secondary topics.
3. Order of secondary topics. Assign headings for secondary topics, as well as headings required to complete standard arrays, in any order following the heading(s) for the major topic(s).