Two definitions: (1) A grouping of occupations having similar working conditions and hazards. Payroll and loss records for these groups are used to establish rates. The National Council on Compensation Insurance (NCCI) uses this data to determine "pure premium" rates for these classes -- i.e. the "break even" rate needed to cover claim costs estimated for each class. (2) The payroll classification(s) assigned to a firm based on the types of work its employees perform