Short guide to subject headings and subdivisions

There are 4 types of subdivisions:

          Topical                     subfield x
           Geographic             subfield z
           Chronological         subfield y
           Form                       subfield v

There are 2 basic orders (minor variations are always possible) of subject strings.

            [Place]  -- [topic] headings    (used for aspects of a place)
           
            [Topic] -- [place] headings (used for topical headings that can be subdivided by place)

Order of subdivisions and meanings of subject strings

             Form subdivision always goes last
             Follow instructions in the manual and subject heading books/files
             The meaning of a string may be tested by constructing a phrase using the elements in reverse                order:   e.g.,

                          Authors, English -- 20th century -- Biography.
                          (A biography of a 20th century English author)

The same elements may express different concepts based on their order:

                          Science -- History -- Periodicals.
                          (A periodical on the history of science)

                          Science -- Periodicals -- History
                          (A history of periodicals in the field of science)

Free-floating subdivisions

     General subdivisions                         H1095
     Persons & ethnic groups                   H1100 & H1103
     Corporate bodies and families          H1105 & H1120
     Place names:                                     H1140 (countries, cities, etc.)
                                                               H1145.5 (bodies of water)
     Pattern headings                               H1146-H1200