Note: If you are using the standard 3rd edition, is titled "Modules over Principal Ideal Domains" (following the structure of rings and fields). Navigating Dummit & Foote Chapter 8: Modules Over PIDs If you have made it to Chapter 8 of Dummit and Foote’s Abstract Algebra , congratulations. You have moved beyond the concrete world of groups and rings and entered the more flexible (and abstract) realm of modules .