An industry is a group of companies that are related to their primary business activities. In modern economies, there are dozens of industry classifications, which are usually classified into large categories called the sector. Individual companies are generally classified into an industry based on their biggest sources of revenue. It is a manufacturing or technologically productive enterprise in a particular area, country, region, or economy, or one of these or any of these. A lone industry is often entitled after its major product; for example, auto industry. For statistical purposes, industries are usually classified according to standard industrial classification (SIC) such as a uniform classification code. Any general business activity or business venture can be separated from others, such as the tourist industry or the entertainment industry.