b'Types of Subject Headings / Form HeadingsHistory1861-1865, Civil War, since not all civil wars are the American Civil War. The termCivil wars could itself become a heading, if it were needed for general materials on rebellions orinternal revolutions.When a single word has several meanings, that word can be used as a subject heading only when itis somehow rendered unambiguous. The word Depression, for example, can mean either aneconomic or a mental state, but as subject headings one is formulated Depressions and the otherDepression (Psychology). Stress can mean either stress on materials or stress on the mind, and thetwo headings are Strength of materials and Stress (Psychology). Notice that the ambiguous wordis qualified even when the other meaning is expressed in other words. Furthermore, an ambiguousterm such as Feedback should be qualified, Feedback (Psychology), even when the other meaning,Feedback (Electronics), does not yet exist in the catalog. Whenever identical words with differentmeanings are used in the catalog, both require a parenthetical qualifier, which is usually either abroader term or discipline of study, as in the case of Seals (Animals) and Seals (Numismatics).In choosing one term as a subject heading from among several possibilities the cataloger must alsothink of the spelling, number, and connotations of the various forms. When variant spellings are inuse, one must be selected and uniformly applied, such as Archeology rather than Archaeology. Adecision also must be made between the singular and plural form, which will be further discussedunder Grammar of Subject Headings below. Sometimes variant forms of words can have differentconnotations, as with Arab, Arabian, and Arabic. It may seem inconsistent to use all three forms insubject headings, but, in fact, they are used consistently in the following ways: Arab relating to thepeople; Arabian referring to the geographical area and to horses; and Arabic for the language, script,or literature.FORM HEADINGSThe second kind of heading that is found in a library catalog is the form heading, which describesnot the subject content of a work but its form. In other words, a form heading tells us not what awork is about but what it is. Form in this context means the intellectual form of the materials ratherthan the physical form of the item, although the physical forms of some nonbook materials, such aspuzzles, sound recordings, or comedy films are also identified by form headings.Some form headings describe the general arrangement of the material and the purpose of the work,such as Almanacs, Atlases, Directories, and Gazetteers. These headings are customarily assignedto individual works as well as to materials about such forms. Theoretically, at least, any form canalso be a topic, since it is possible for someone to write a book about almanacs or gazetteers.Other form headings are the names of literary forms and genres. Headings for the major literaryforms, Fiction, Poetry, Drama, and Essays, are usually used as topical subject headings. As formheadings they are used for collections only rather than for individual literary works. Minor literaryforms, also known as genres, such as Science fiction, Epistolary poetry, and Childrens plays, areA-24'