Cutter’s Expansive Classification (CEC) is a system for organizing library materials that was developed by Charles Ammi Cutter in the 19th century. It is based on the principle that library materials should be organized in such a way that related items are grouped together. Cutter’s Expansive Classification uses a combination of letters and numbers to represent different subjects, and it is arranged in a hierarchy with more specific subjects being nested within broader ones. The CEC system is no longer widely used in libraries, but it has influenced the development of other library classification systems.