Dow Jones index symbols are abbreviations of up to four letters that represent the companies listed on the Dow Jones Industrial Average stock market index. As of February 2015, there are 30 major American companies that are listed on the Dow Jones and have index symbols.
The company index symbols range from one to four letters that represent the company name. For example, McDonalds is MCD, 3M is MMM and the Walt Disney Company is DIS. The companies listed on the Dow Jones are usually the largest in the United States. These companies collectively represent about 25 percent of all stock trading on any given day.