b'Classification and Subject HeadingsThe cataloger should recognize a fundamental difference between classification and subjectheadings for the library catalog. In any system of classification that determines the arrangement ofitems on the shelves, a work can obviously have only one class number and stand in only one place,but in a catalog the same work can be entered, if necessary, under as many different points of entryas there are distinct subjects in the work (usually, however, not more than three). Classification isused to gather in one numerical place on the shelf works that give similar treatment to a subject.Subject headings gather in one alphabetical place in a catalog all treatments of a subject regardlessof shelf location.Another difference between classification and subject cataloging is that classification is frequentlyless precise than the subject entries for the catalog. Material on floriculture in general as well as onspecific kinds of garden flowers are classed together in 635.9 in the Dewey Decimal Classification.A book on flower gardening, one on perennial gardening, and one on rose gardening will all threebe classified in one number, while in the catalog each book will have its own specific subjectheading: Flower gardening, Perennials, or Roses.Library materials are classified by discipline, not by subject. Asingle subject may be dealt with inmany disciplines. The Dewey classification numbers given with a heading in the Sears List areintended only to direct the cataloger to the disciplines where that subject is most likely to be treated.They are not meant to be absolute or cover all possibilities and should be used together with theDewey Decimal Classification schedules. The cataloger must examine the work at hand anddetermine the discipline in which the author is writing. On the basis of that decision the catalogerclassifies the work, not by the subject of the work alone.A-42'