Industry is the production of an economic good or service within an economy. Manufacturing industry became a key sector of production and labour in European and North American countries during the Industrial Revolution, upsetting previous mercantile and feudal economies. This occurred through many successive rapid advances in technology, such as the production of steel and coal. Following the Industrial Revolution, perhaps a third of the world’s economic output is derived from manufacturing industries. Many developed countries and many developing/semi-developed countries (People’s Republic of China, India etc.) depend significantly on industry. Industries, the countries they reside in, and the economies of those countries are interlinked in a complex web of interdependence.

Industries can be classified in a variety of ways. At the top level, industry is often classified into sectors: Primary or extractive, secondary or manufacturing, and tertiary or services. Some authors add quaternary (knowledge) or even quinary (culture and research) sectors. Over time, the fraction of a society’s industry within each sector changes.

There are many other different kinds of industries, and often organized into different classes or sectors by a variety of industrial classifications. Market-based classification systems such as the Global Industry Classification Standard and the Industry Classification Benchmark are used in finance and market research. These classification systems commonly divide industries according to similar functions and markets and identify businesses producing related products. Industries can also be identified by product, such as: chemical industry, petroleum industry, automotive industry, electronic industry, meatpacking industry, hospitality industry, food industry, fish industry, software industry, paper industry, entertainment industry, semiconductor industry, cultural industry, and poverty industry.