An industry classification system is a means of categorizing industries so that similar industries are grouped together and narrower industries appear within broader categories. Most company databases offer industry screening by classification system as well as by key words in the business description. Screening in a company database by use of an industrial classification system such as NAICS or SIC (see below can result in more comprehensive results than key word searching as many descriptions are incomplete or may be absent from a database.
On the other hand industry classification systems do not keep up with industry trends (Ex: wearables, big data) so new buzz words are not captured. For this reason a combination of approaches usually yields the best results.
The resources listed below can be helpful in identifying the code to use for a company search by industry.