Free-floating subdivisions are non-geographic concepts that can be added to headings. Until 2003, they were contained in the green Subject Headings Manual, but they are now included in the red books; they are also available in a separate print publication, Free-floating Subdivisions: an alphabetical index, and they are searchable as a separate database within the online LCSH. The print version is now in its 23rd edition (2011), and unfortunately this will be the last.

We saw in Chapter 6 on content analysis that some varieties of concept occur very frequently in the subjects of documents: concepts such as place, time, form and persons, the last often as the intended readership. In classification systems these very common ideas are usually contained in special auxiliary tables, represented by codes which can be attached to classmarks, sometimes using particular symbols or facet indicators to indicate that an auxiliary concept is present. In LCSH a similar purpose is served by the free-floating subdivisions. The idea of the free-floating subdivision is that it can be used without any specific instruction, and attached to main headings as required. Some can be added to any heading, whereas others are restricted to particular types of heading, such as those for individual authors which are used to specify the different texts and editions and secondary publications associated with an author.

Free-floating subdivisions are added to main headings using the double dash in exactly the same way as topical and geographic subdivisions. Conveniently, the dashes are included in the subdivisions as they are displayed in the alphabetical list in Classification Web. The subdivisions are also accompanied by copious notes explaining the way in which individual subdivisions are to be used:

–Classification

–Editions, Curious

–Kings and rulers

–Semantics