Which classification system is used to categorize the design of removable partial dentures (RPDs) based on the relationship of the edentulous areas?

The Kennedy Classification (developed by Edward Kennedy in 1925) is the universally accepted system for classifying removable partial denture (RPD) designs based on the location of edentulous areas relative to remaining teeth. It has four major classes: Class I (bilateral edentulous areas posterior to all remaining teeth — free-end saddles); Class II (unilateral edentulous area posterior to remaining teeth); Class III (unilateral edentulous area with natural teeth on both sides); Class IV (single edentulous area crossing the midline anteriorly). Applegate's eight rules are the modifying rules applied to the Kennedy classification to allow for additional edentulous areas. The Kennedy classification is the basis, while Applegate's rules modify it.