1st definition from businessdictionary.com: Network of commercial organizations (such as manufacturers, producers, wholesalers, retailers, and buyers) who generate, distribute, and purchase goods and services. See also financial institutions.
2nd definition from econlib.org: 1. Specific agencies or foundations, both government and private, devoted to collecting or studying economic data, or commissioned with the job of supplying a good or service that is important to the economy of a country. The Internal Revenue Service (the IRS—the government tax-collection agency), the U.S. Federal Reserve (the government producer of money), the National Bureau of Economic Research (a private research agency) are all examples of economic institutions. 2. Well-established arrangements and structures that are part of the culture or society, e.g., competitive markets, the banking system, kids' allowances, customary tipping, and a system of property rights are examples of economic institutions.
Which one is correct? Also, on wikipedia it says businesses are a part of institutions. https://en.wikipedia.org/wiki/Institution