The current paper discusses a fundamentally new approach to defining and finding interactions in computer-aided design (CAD) forms or features. The paper provides a classification of the various interactions found among CAD forms. The paper also illustrates a robust approach to defining and recognizing stand-alone as well as interacting forms. The problem of generic form definition is resolved using a set of high-level abstract entities called loops and links. The computational difficulty in finding the forms is resolved using a mathematically defined geometric filter called the Differential Depth Filter.