A user-defined word is a COBOL word that is created by the programmer. Except for section-names, paragraph-names, segment-numbers, and level-numbers, all user-defined words must contain at least one alphabetic character. User-defined words may not be any of the reserved words.
All user-defined words must be unique except as specified in the rules for uniqueness of reference. However, segment-numbers and level-numbers need not be unique.