The North American Industry Classification System is used to organize industry information. It's designed to produce common industry definitions for Canada, Mexico, and the United States. It is a hierarchical classification system, offering five levels of detail.
Industries are represented by a six-digit number. The first two digits designate the economic sector: manufacturing, agriculture, wholesale, retail, professional services, etc. The subsequent digits designate subsectors and industry groups.
Each digit in the code is part of a series of progressively narrower categories.
44 - Retail
448 - Clothing and Clothing Accessories Stores
4481 - Clothing Stores
448140 - Family Clothing Stores
The Standard Industrial Classification, an earlier U.S. system, is still used by some sources.
Government agencies and business information providers use NAICS to organize industry information. In addition to the links below, you can search several business databases by NAICS and/or SIC codes for industry information.
Note that companies that do more than one type of business may have multiple codes.