According to 4.2b of GB/T 1.1-2020 "Directives for Standardization - Part 1: Structure and Drafting Rules for Standardization Documents", a classification standard refers to "a standard that makes a regular arrangement of products, processes or services or establishes a classification system based on similar characteristics such as origin, composition, performance or purpose".

The function of a classification standard is to "establish" a classification system, and its core technical elements are "classification and/or coding". The result of classification is specific categories/items. These categories/items can be identified by named names (composed of words) or assigned codes (composed of Arabic numerals, Latin letters or a combination of them).

The structure of classification standards, classification principles, classification methods, naming and coding methods, coding expressions, as well as the detailed rules for compiling classification tables and code tables, etc are specified in GB/T 20001.3-2015 "Rules for Preparing Standards - Part 3: Classification Standards".