"Industry classification or industry taxonomy organizes companies into industrial groupings based on similar production processes, similar products, or similar behavior in financial markets. A wide variety of taxonomies is in use, sponsored by different organizations and based on different criteria."
Note: In the United States the SIC code is being supplanted by the six-digit North American Industry Classification System (NAICS code), which was released in 1997; however certain government departments and agencies, such as the U.S. Securities and Exchange Commission (SEC), still use the SIC codes.