1. Definition: A union catalogue list in one sequence the holding or part of holdings of two or more libraries. According to William A. Katz, a union catalogue is an “inventory common to several libraries and listing some or all of their publications maintained in one or more orders of arrangements.” Union catalogues generally uses some location symbol for each and every libraries whose collection are included in the union catalogue for easy location of documents.
2. Types: We may recognize local, regional and national union catalogue. Further division may be done on the basis of the kinds of material include i.e. book, periodical, film, etc.
3. Functions: The functions of union catalogues are
i) Union catalogue serves as a locating tool for the document.
ii) It helps in identifying a given document for which bibliographic information is provided.
iii) It helps in interlibrary loan.
iv) It helps in selection of documents.
v) It helps to achieve coordination in the acquisition and selection programme of a group of libraries. It helps to avoid unnecessary duplication of material like periodicals, etc.
vi) It serve as a list of total document resource of libraries in a given geographical region.
4. Example: IndCat: Online Union Catalogue of Indian Universities, INFLIBNET, Available over: http://indcat.inflibnet.ac.in/indcat/book.jsp