In library science, authority control is a process that organizes bibliographic information, for example in library catalogs by using a single, distinct spelling of a name (heading) or a numeric identifier for each topic. The word "authority" in "authority control" derives from the idea that the names of people, places, things, and concepts are "authorized," i.e., they are established in one particular form. These one-of-a-kind headings or identifiers are applied consistently throughout catalogs which make use of the respective authority file, and are applied for other methods of organizing data such as linkages and cross references. Each controlled entry is described in an authority "record" in terms of its scope and usage, and this organization helps the library staff maintain the catalog and make it user-friendly for researchers.