The term 'FORTUNE 500 ABBR.' refers to the abbreviations used for the Fortune 500, a list of the 500 largest companies in the United States as measured by their gross revenue. The two abbreviations used are CORP (4 letters) and INC (3 letters). CORP stands for Corporation, which is a type of business entity that is owned by shareholders and managed by a board of directors. INC stands for Incorporated, which is a type of business entity that is owned by shareholders and managed by a board of directors, but with limited liability for its owners.