What Is Industry ?

Industry, group of productive enterprises or organizations that produce or supply goods, services, or sources of income. In economics, industries are generally classified as primary, secondary, tertiary, and quaternary; secondary industries are further classified as heavy and light.

Second Defination :

Many people think of industry as the collective large-scale manufacturing of goods in well-organized plants with a high degree of automation and specialization. Although this is a common example of industry, it can also include other commercial activities that provide goods and services such as agriculture, transportation, hospitality, and many others. 

Third Defination :

An industry is a group of companies that are related based on their primary business activities. In modern economies, there are dozens of industry classifications. Industry classifications are typically grouped into larger categories called sectors.

Individual companies are generally classified into an industry based on their largest sources of revenue. 

For example, 
while an automobile manufacturer might have a financing division that contributes 10% to the firm's overall revenues, the company would be classified in the automaker industry by most classification systems.