b'Types of Subject HeadingsThere are four types of subject headings: topical headings, form headings, geographic headings, andproper names.TOPICAL HEADINGSTopical subject headings are simply the words or phrases for common things or concepts thatrepresent the content of various works. In choosing the word or phrase that makes the best subjectheading several things should be considered. The first and most obvious is the literary warrant, orthe language of the material being cataloged. The word most commonly used in the literature ismost likely the word that best represents the item cataloged. If nine out of ten books on the subjectuse the phrase Gun control, there is no reason to use any word or phrase other than Gun controlas a subject heading, so long as that phrase meets certain other criteria.A second consideration, and one of the criteria that a subject heading should meet, is that ofcommon usage. In so far as possible a subject heading should represent the common usage of theEnglish language. In American libraries this means current American spelling and terminology:Labor not Labour; Elevators not Lifts. (In British libraries these choices would be reversed.)Foreign terms such as Film noir are not used unless they have been fully incorporated into theEnglish language. By the same token contemporary usage gradually should replace antiquatedwords or phrases. The heading Blacks, for example, replaced Negroes as common usage changed.In time the heading African Americans was added to the Sears List for greater specificity, as theuse of that term stabilized. What is common usage depends, in part, upon who the users of a libraryare. In most small libraries the popular or common word for a thing is to be preferred to thescientific or technical word, when the two are truly synonymous. For example, Desert animals ispreferable in most small libraries to Desert fauna. In such a case the scientific term should be a Seereference to the established term.In order to maintain uniformity in a library catalog two things are necessary. The first is abiding byCutters rule of specificity, and the second is choosing a single word or phrase from among itssynonyms or near-synonyms in establishing a subject heading. If Desert animals and Desert faunawere both allowed as established headings, the material on one subject would end up in two places.Sometimes a single word or phrase must be chosen from among several choices that do not meanexactly the same thing but are too close to be easily distinguished. In the Sears List, for example,Regional planning is an established heading with See references from County planning,Metropolitan planning, and State planning. The term chosen as the established heading is the onethat is most inclusive.Another important consideration in establishing topical subject headings is that they should be clearand unambiguous. Sometimes the most common term for a topic is not suitable as a subject headingbecause it is ambiguous. Civil War, for example, must be rejected in favor of United States A-23'