organisation, organization, arrangement, system - an organized structure for arranging or classifying; "he changed the arrangement of the topics"; "the facts were familiar but it was in the organization of them that he was original"; "he tried to understand their system of classification"

decimal system of classification, Dewey decimal classification, Dewey decimal system - a system used by libraries to classify nonfictional publications into subject categories; the subject is indicated by a three-digit numeral and further specification is given by numerals following a decimal point; publications are shelved by number

hierarchical classification system - a classification system where entries are arranged based on some hierarchical structure

file system, filing system - a system of classifying into files (usually arranged alphabetically)

pigeonholing, grouping - a system for classifying things into groups

rating system, scoring system - a system of classifying according to quality or merit or amount

ABO blood group system, ABO group, ABO system - a classification system for the antigens of human blood; used in blood transfusion therapy; four groups are A and B and AB and O