[[Image:HK Wan Chai Library Inside Bookcase a.jpg|thumb|A library book shelf in Hong Kong arranged using the Dewey classification]]
A '''library classification''' is structuresystem of organization of knowledge in which sources are arranged according to the classification scheme and ordered very systematically. Library classifications are a notational system that represents the order of topics in the classification and allows items to be stored in the order of classification. Library classification systems group related materials together, typically arranged as a hierarchical tree structure. A different kind of classification system, called a [[faceted classification]]<ref>{{Cite book|last=Publius|first=Vergilius Maro|url=http://worldcat.org/oclc/475463360|title=P. Virgilii Maronis Opera|date=1900|oclc=475463360}}</ref> system, is also widely used, which allows the assignment of multiple classifications to an object, enabling the classifications to be ordered in many ways.
