1. A proper name (or its abbreviation or acronym) of an institution, person, place, object, or process, optionally treated as a category of heading distinct from terms. Identifiers may be held in a separate file (compare authority file), and their form may be controlled (e.g., the name of an international organization having different names in various languages, only one of which is selected). 2. In some systems, a provisional term that may be upgraded to approved status, or a highly specific term that is not eligible for term status, but which is considered useful for retrieval and is assigned to one or more content objects without vocabulary control.